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![Junio C Hamano](/assets/img/avatar_default.png)
Teach and encourage first-time contributors to this project to state the base commit when they submit their topic. * jc/tutorial-format-patch-base: MyFirstContribution: teach to use "format-patch --base=auto"
1268 lines
48 KiB
Plaintext
1268 lines
48 KiB
Plaintext
My First Contribution to the Git Project
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========================================
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:sectanchors:
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[[summary]]
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== Summary
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This is a tutorial demonstrating the end-to-end workflow of creating a change to
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the Git tree, sending it for review, and making changes based on comments.
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[[prerequisites]]
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=== Prerequisites
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This tutorial assumes you're already fairly familiar with using Git to manage
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source code. The Git workflow steps will largely remain unexplained.
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[[related-reading]]
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=== Related Reading
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This tutorial aims to summarize the following documents, but the reader may find
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useful additional context:
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- `Documentation/SubmittingPatches`
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- `Documentation/howto/new-command.txt`
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[[getting-help]]
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=== Getting Help
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If you get stuck, you can seek help in the following places.
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==== git@vger.kernel.org
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This is the main Git project mailing list where code reviews, version
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announcements, design discussions, and more take place. Those interested in
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contributing are welcome to post questions here. The Git list requires
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plain-text-only emails and prefers inline and bottom-posting when replying to
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mail; you will be CC'd in all replies to you. Optionally, you can subscribe to
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the list by sending an email to majordomo@vger.kernel.org with "subscribe git"
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in the body. The https://lore.kernel.org/git[archive] of this mailing list is
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available to view in a browser.
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==== https://groups.google.com/forum/#!forum/git-mentoring[git-mentoring@googlegroups.com]
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This mailing list is targeted to new contributors and was created as a place to
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post questions and receive answers outside of the public eye of the main list.
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Veteran contributors who are especially interested in helping mentor newcomers
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are present on the list. In order to avoid search indexers, group membership is
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required to view messages; anyone can join and no approval is required.
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==== https://web.libera.chat/#git-devel[#git-devel] on Libera Chat
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This IRC channel is for conversations between Git contributors. If someone is
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currently online and knows the answer to your question, you can receive help
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in real time. Otherwise, you can read the
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https://colabti.org/irclogger/irclogger_logs/git-devel[scrollback] to see
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whether someone answered you. IRC does not allow offline private messaging, so
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if you try to private message someone and then log out of IRC, they cannot
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respond to you. It's better to ask your questions in the channel so that you
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can be answered if you disconnect and so that others can learn from the
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conversation.
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[[getting-started]]
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== Getting Started
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[[cloning]]
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=== Clone the Git Repository
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Git is mirrored in a number of locations. Clone the repository from one of them;
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https://git-scm.com/downloads suggests one of the best places to clone from is
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the mirror on GitHub.
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----
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$ git clone https://github.com/git/git git
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$ cd git
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----
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[[dependencies]]
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=== Installing Dependencies
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To build Git from source, you need to have a handful of dependencies installed
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on your system. For a hint of what's needed, you can take a look at
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`INSTALL`, paying close attention to the section about Git's dependencies on
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external programs and libraries. That document mentions a way to "test-drive"
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our freshly built Git without installing; that's the method we'll be using in
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this tutorial.
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Make sure that your environment has everything you need by building your brand
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new clone of Git from the above step:
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----
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$ make
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----
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NOTE: The Git build is parallelizable. `-j#` is not included above but you can
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use it as you prefer, here and elsewhere.
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[[identify-problem]]
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=== Identify Problem to Solve
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////
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Use + to indicate fixed-width here; couldn't get ` to work nicely with the
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quotes around "Pony Saying 'Um, Hello'".
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////
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In this tutorial, we will add a new command, +git psuh+, short for ``Pony Saying
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`Um, Hello''' - a feature which has gone unimplemented despite a high frequency
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of invocation during users' typical daily workflow.
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(We've seen some other effort in this space with the implementation of popular
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commands such as `sl`.)
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[[setup-workspace]]
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=== Set Up Your Workspace
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Let's start by making a development branch to work on our changes. Per
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`Documentation/SubmittingPatches`, since a brand new command is a new feature,
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it's fine to base your work on `master`. However, in the future for bugfixes,
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etc., you should check that document and base it on the appropriate branch.
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For the purposes of this document, we will base all our work on the `master`
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branch of the upstream project. Create the `psuh` branch you will use for
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development like so:
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----
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$ git checkout -b psuh origin/master
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----
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We'll make a number of commits here in order to demonstrate how to send a topic
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with multiple patches up for review simultaneously.
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[[code-it-up]]
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== Code It Up!
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NOTE: A reference implementation can be found at
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https://github.com/nasamuffin/git/tree/psuh.
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[[add-new-command]]
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=== Adding a New Command
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Lots of the subcommands are written as builtins, which means they are
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implemented in C and compiled into the main `git` executable. Implementing the
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very simple `psuh` command as a built-in will demonstrate the structure of the
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codebase, the internal API, and the process of working together as a contributor
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with the reviewers and maintainer to integrate this change into the system.
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Built-in subcommands are typically implemented in a function named "cmd_"
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followed by the name of the subcommand, in a source file named after the
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subcommand and contained within `builtin/`. So it makes sense to implement your
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command in `builtin/psuh.c`. Create that file, and within it, write the entry
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point for your command in a function matching the style and signature:
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----
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int cmd_psuh(int argc, const char **argv, const char *prefix)
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----
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We'll also need to add the declaration of psuh; open up `builtin.h`, find the
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declaration for `cmd_pull`, and add a new line for `psuh` immediately before it,
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in order to keep the declarations alphabetically sorted:
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----
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int cmd_psuh(int argc, const char **argv, const char *prefix);
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----
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Be sure to `#include "builtin.h"` in your `psuh.c`.
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Go ahead and add some throwaway printf to that function. This is a decent
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starting point as we can now add build rules and register the command.
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NOTE: Your throwaway text, as well as much of the text you will be adding over
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the course of this tutorial, is user-facing. That means it needs to be
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localizable. Take a look at `po/README` under "Marking strings for translation".
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Throughout the tutorial, we will mark strings for translation as necessary; you
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should also do so when writing your user-facing commands in the future.
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----
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int cmd_psuh(int argc, const char **argv, const char *prefix)
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{
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printf(_("Pony saying hello goes here.\n"));
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return 0;
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}
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----
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Let's try to build it. Open `Makefile`, find where `builtin/pull.o` is added
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to `BUILTIN_OBJS`, and add `builtin/psuh.o` in the same way next to it in
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alphabetical order. Once you've done so, move to the top-level directory and
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build simply with `make`. Also add the `DEVELOPER=1` variable to turn on
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some additional warnings:
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----
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$ echo DEVELOPER=1 >config.mak
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$ make
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----
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NOTE: When you are developing the Git project, it's preferred that you use the
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`DEVELOPER` flag; if there's some reason it doesn't work for you, you can turn
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it off, but it's a good idea to mention the problem to the mailing list.
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Great, now your new command builds happily on its own. But nobody invokes it.
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Let's change that.
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The list of commands lives in `git.c`. We can register a new command by adding
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a `cmd_struct` to the `commands[]` array. `struct cmd_struct` takes a string
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with the command name, a function pointer to the command implementation, and a
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setup option flag. For now, let's keep mimicking `push`. Find the line where
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`cmd_push` is registered, copy it, and modify it for `cmd_psuh`, placing the new
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line in alphabetical order (immediately before `cmd_pull`).
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The options are documented in `builtin.h` under "Adding a new built-in." Since
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we hope to print some data about the user's current workspace context later,
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we need a Git directory, so choose `RUN_SETUP` as your only option.
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Go ahead and build again. You should see a clean build, so let's kick the tires
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and see if it works. There's a binary you can use to test with in the
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`bin-wrappers` directory.
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----
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$ ./bin-wrappers/git psuh
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----
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Check it out! You've got a command! Nice work! Let's commit this.
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`git status` reveals modified `Makefile`, `builtin.h`, and `git.c` as well as
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untracked `builtin/psuh.c` and `git-psuh`. First, let's take care of the binary,
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which should be ignored. Open `.gitignore` in your editor, find `/git-pull`, and
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add an entry for your new command in alphabetical order:
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----
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...
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/git-prune-packed
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/git-psuh
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/git-pull
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/git-push
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/git-quiltimport
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/git-range-diff
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...
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----
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Checking `git status` again should show that `git-psuh` has been removed from
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the untracked list and `.gitignore` has been added to the modified list. Now we
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can stage and commit:
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----
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$ git add Makefile builtin.h builtin/psuh.c git.c .gitignore
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$ git commit -s
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----
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You will be presented with your editor in order to write a commit message. Start
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the commit with a 50-column or less subject line, including the name of the
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component you're working on, followed by a blank line (always required) and then
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the body of your commit message, which should provide the bulk of the context.
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Remember to be explicit and provide the "Why" of your change, especially if it
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couldn't easily be understood from your diff. When editing your commit message,
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don't remove the `Signed-off-by` trailer which was added by `-s` above.
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----
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psuh: add a built-in by popular demand
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Internal metrics indicate this is a command many users expect to be
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present. So here's an implementation to help drive customer
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satisfaction and engagement: a pony which doubtfully greets the user,
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or, a Pony Saying "Um, Hello" (PSUH).
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This commit message is intentionally formatted to 72 columns per line,
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starts with a single line as "commit message subject" that is written as
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if to command the codebase to do something (add this, teach a command
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that). The body of the message is designed to add information about the
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commit that is not readily deduced from reading the associated diff,
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such as answering the question "why?".
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Signed-off-by: A U Thor <author@example.com>
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----
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Go ahead and inspect your new commit with `git show`. "psuh:" indicates you
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have modified mainly the `psuh` command. The subject line gives readers an idea
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of what you've changed. The sign-off line (`-s`) indicates that you agree to
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the Developer's Certificate of Origin 1.1 (see the
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`Documentation/SubmittingPatches` +++[[dco]]+++ header).
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For the remainder of the tutorial, the subject line only will be listed for the
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sake of brevity. However, fully-fleshed example commit messages are available
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on the reference implementation linked at the top of this document.
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[[implementation]]
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=== Implementation
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It's probably useful to do at least something besides printing out a string.
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Let's start by having a look at everything we get.
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Modify your `cmd_psuh` implementation to dump the args you're passed, keeping
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existing `printf()` calls in place:
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----
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int i;
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...
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printf(Q_("Your args (there is %d):\n",
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"Your args (there are %d):\n",
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argc),
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argc);
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for (i = 0; i < argc; i++)
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printf("%d: %s\n", i, argv[i]);
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printf(_("Your current working directory:\n<top-level>%s%s\n"),
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prefix ? "/" : "", prefix ? prefix : "");
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----
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Build and try it. As you may expect, there's pretty much just whatever we give
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on the command line, including the name of our command. (If `prefix` is empty
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for you, try `cd Documentation/ && ../bin-wrappers/git psuh`). That's not so
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helpful. So what other context can we get?
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Add a line to `#include "config.h"`. Then, add the following bits to the
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function body:
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----
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const char *cfg_name;
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...
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git_config(git_default_config, NULL);
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if (git_config_get_string_tmp("user.name", &cfg_name) > 0)
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printf(_("No name is found in config\n"));
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else
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printf(_("Your name: %s\n"), cfg_name);
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----
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`git_config()` will grab the configuration from config files known to Git and
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apply standard precedence rules. `git_config_get_string_tmp()` will look up
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a specific key ("user.name") and give you the value. There are a number of
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single-key lookup functions like this one; you can see them all (and more info
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about how to use `git_config()`) in `Documentation/technical/api-config.txt`.
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You should see that the name printed matches the one you see when you run:
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----
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$ git config --get user.name
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----
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Great! Now we know how to check for values in the Git config. Let's commit this
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too, so we don't lose our progress.
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----
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$ git add builtin/psuh.c
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$ git commit -sm "psuh: show parameters & config opts"
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----
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NOTE: Again, the above is for sake of brevity in this tutorial. In a real change
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you should not use `-m` but instead use the editor to write a meaningful
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message.
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Still, it'd be nice to know what the user's working context is like. Let's see
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if we can print the name of the user's current branch. We can mimic the
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`git status` implementation; the printer is located in `wt-status.c` and we can
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see that the branch is held in a `struct wt_status`.
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`wt_status_print()` gets invoked by `cmd_status()` in `builtin/commit.c`.
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Looking at that implementation we see the status config being populated like so:
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----
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status_init_config(&s, git_status_config);
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----
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But as we drill down, we can find that `status_init_config()` wraps a call
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to `git_config()`. Let's modify the code we wrote in the previous commit.
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Be sure to include the header to allow you to use `struct wt_status`:
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----
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#include "wt-status.h"
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----
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Then modify your `cmd_psuh` implementation to declare your `struct wt_status`,
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prepare it, and print its contents:
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----
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struct wt_status status;
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...
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wt_status_prepare(the_repository, &status);
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git_config(git_default_config, &status);
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...
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printf(_("Your current branch: %s\n"), status.branch);
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----
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Run it again. Check it out - here's the (verbose) name of your current branch!
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Let's commit this as well.
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----
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$ git add builtin/psuh.c
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$ git commit -sm "psuh: print the current branch"
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----
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Now let's see if we can get some info about a specific commit.
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Luckily, there are some helpers for us here. `commit.h` has a function called
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`lookup_commit_reference_by_name` to which we can simply provide a hardcoded
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string; `pretty.h` has an extremely handy `pp_commit_easy()` call which doesn't
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require a full format object to be passed.
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Add the following includes:
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----
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#include "commit.h"
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#include "pretty.h"
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----
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Then, add the following lines within your implementation of `cmd_psuh()` near
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the declarations and the logic, respectively.
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----
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struct commit *c = NULL;
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struct strbuf commitline = STRBUF_INIT;
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...
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c = lookup_commit_reference_by_name("origin/master");
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if (c != NULL) {
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pp_commit_easy(CMIT_FMT_ONELINE, c, &commitline);
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printf(_("Current commit: %s\n"), commitline.buf);
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}
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----
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The `struct strbuf` provides some safety belts to your basic `char*`, one of
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which is a length member to prevent buffer overruns. It needs to be initialized
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nicely with `STRBUF_INIT`. Keep it in mind when you need to pass around `char*`.
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`lookup_commit_reference_by_name` resolves the name you pass it, so you can play
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with the value there and see what kind of things you can come up with.
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`pp_commit_easy` is a convenience wrapper in `pretty.h` that takes a single
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format enum shorthand, rather than an entire format struct. It then
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pretty-prints the commit according to that shorthand. These are similar to the
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formats available with `--pretty=FOO` in many Git commands.
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Build it and run, and if you're using the same name in the example, you should
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see the subject line of the most recent commit in `origin/master` that you know
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about. Neat! Let's commit that as well.
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----
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$ git add builtin/psuh.c
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$ git commit -sm "psuh: display the top of origin/master"
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----
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[[add-documentation]]
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=== Adding Documentation
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Awesome! You've got a fantastic new command that you're ready to share with the
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community. But hang on just a minute - this isn't very user-friendly. Run the
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following:
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----
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$ ./bin-wrappers/git help psuh
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----
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Your new command is undocumented! Let's fix that.
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Take a look at `Documentation/git-*.txt`. These are the manpages for the
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subcommands that Git knows about. You can open these up and take a look to get
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acquainted with the format, but then go ahead and make a new file
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`Documentation/git-psuh.txt`. Like with most of the documentation in the Git
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project, help pages are written with AsciiDoc (see CodingGuidelines, "Writing
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Documentation" section). Use the following template to fill out your own
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manpage:
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// Surprisingly difficult to embed AsciiDoc source within AsciiDoc.
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[listing]
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....
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git-psuh(1)
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===========
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NAME
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----
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git-psuh - Delight users' typo with a shy horse
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SYNOPSIS
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--------
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[verse]
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'git-psuh [<arg>...]'
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DESCRIPTION
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-----------
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...
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OPTIONS[[OPTIONS]]
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------------------
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...
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OUTPUT
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------
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...
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GIT
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---
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Part of the linkgit:git[1] suite
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....
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The most important pieces of this to note are the file header, underlined by =,
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the NAME section, and the SYNOPSIS, which would normally contain the grammar if
|
|
your command took arguments. Try to use well-established manpage headers so your
|
|
documentation is consistent with other Git and UNIX manpages; this makes life
|
|
easier for your user, who can skip to the section they know contains the
|
|
information they need.
|
|
|
|
NOTE: Before trying to build the docs, make sure you have the package `asciidoc`
|
|
installed.
|
|
|
|
Now that you've written your manpage, you'll need to build it explicitly. We
|
|
convert your AsciiDoc to troff which is man-readable like so:
|
|
|
|
----
|
|
$ make all doc
|
|
$ man Documentation/git-psuh.1
|
|
----
|
|
|
|
or
|
|
|
|
----
|
|
$ make -C Documentation/ git-psuh.1
|
|
$ man Documentation/git-psuh.1
|
|
----
|
|
|
|
While this isn't as satisfying as running through `git help`, you can at least
|
|
check that your help page looks right.
|
|
|
|
You can also check that the documentation coverage is good (that is, the project
|
|
sees that your command has been implemented as well as documented) by running
|
|
`make check-docs` from the top-level.
|
|
|
|
Go ahead and commit your new documentation change.
|
|
|
|
[[add-usage]]
|
|
=== Adding Usage Text
|
|
|
|
Try and run `./bin-wrappers/git psuh -h`. Your command should crash at the end.
|
|
That's because `-h` is a special case which your command should handle by
|
|
printing usage.
|
|
|
|
Take a look at `Documentation/technical/api-parse-options.txt`. This is a handy
|
|
tool for pulling out options you need to be able to handle, and it takes a
|
|
usage string.
|
|
|
|
In order to use it, we'll need to prepare a NULL-terminated array of usage
|
|
strings and a `builtin_psuh_options` array.
|
|
|
|
Add a line to `#include "parse-options.h"`.
|
|
|
|
At global scope, add your array of usage strings:
|
|
|
|
----
|
|
static const char * const psuh_usage[] = {
|
|
N_("git psuh [<arg>...]"),
|
|
NULL,
|
|
};
|
|
----
|
|
|
|
Then, within your `cmd_psuh()` implementation, we can declare and populate our
|
|
`option` struct. Ours is pretty boring but you can add more to it if you want to
|
|
explore `parse_options()` in more detail:
|
|
|
|
----
|
|
struct option options[] = {
|
|
OPT_END()
|
|
};
|
|
----
|
|
|
|
Finally, before you print your args and prefix, add the call to
|
|
`parse-options()`:
|
|
|
|
----
|
|
argc = parse_options(argc, argv, prefix, options, psuh_usage, 0);
|
|
----
|
|
|
|
This call will modify your `argv` parameter. It will strip the options you
|
|
specified in `options` from `argv` and the locations pointed to from `options`
|
|
entries will be updated. Be sure to replace your `argc` with the result from
|
|
`parse_options()`, or you will be confused if you try to parse `argv` later.
|
|
|
|
It's worth noting the special argument `--`. As you may be aware, many Unix
|
|
commands use `--` to indicate "end of named parameters" - all parameters after
|
|
the `--` are interpreted merely as positional arguments. (This can be handy if
|
|
you want to pass as a parameter something which would usually be interpreted as
|
|
a flag.) `parse_options()` will terminate parsing when it reaches `--` and give
|
|
you the rest of the options afterwards, untouched.
|
|
|
|
Now that you have a usage hint, you can teach Git how to show it in the general
|
|
command list shown by `git help git` or `git help -a`, which is generated from
|
|
`command-list.txt`. Find the line for 'git-pull' so you can add your 'git-psuh'
|
|
line above it in alphabetical order. Now, we can add some attributes about the
|
|
command which impacts where it shows up in the aforementioned help commands. The
|
|
top of `command-list.txt` shares some information about what each attribute
|
|
means; in those help pages, the commands are sorted according to these
|
|
attributes. `git psuh` is user-facing, or porcelain - so we will mark it as
|
|
"mainporcelain". For "mainporcelain" commands, the comments at the top of
|
|
`command-list.txt` indicate we can also optionally add an attribute from another
|
|
list; since `git psuh` shows some information about the user's workspace but
|
|
doesn't modify anything, let's mark it as "info". Make sure to keep your
|
|
attributes in the same style as the rest of `command-list.txt` using spaces to
|
|
align and delineate them:
|
|
|
|
----
|
|
git-prune-packed plumbingmanipulators
|
|
git-psuh mainporcelain info
|
|
git-pull mainporcelain remote
|
|
git-push mainporcelain remote
|
|
----
|
|
|
|
Build again. Now, when you run with `-h`, you should see your usage printed and
|
|
your command terminated before anything else interesting happens. Great!
|
|
|
|
Go ahead and commit this one, too.
|
|
|
|
[[testing]]
|
|
== Testing
|
|
|
|
It's important to test your code - even for a little toy command like this one.
|
|
Moreover, your patch won't be accepted into the Git tree without tests. Your
|
|
tests should:
|
|
|
|
* Illustrate the current behavior of the feature
|
|
* Prove the current behavior matches the expected behavior
|
|
* Ensure the externally-visible behavior isn't broken in later changes
|
|
|
|
So let's write some tests.
|
|
|
|
Related reading: `t/README`
|
|
|
|
[[overview-test-structure]]
|
|
=== Overview of Testing Structure
|
|
|
|
The tests in Git live in `t/` and are named with a 4-digit decimal number using
|
|
the schema shown in the Naming Tests section of `t/README`.
|
|
|
|
[[write-new-test]]
|
|
=== Writing Your Test
|
|
|
|
Since this a toy command, let's go ahead and name the test with t9999. However,
|
|
as many of the family/subcmd combinations are full, best practice seems to be
|
|
to find a command close enough to the one you've added and share its naming
|
|
space.
|
|
|
|
Create a new file `t/t9999-psuh-tutorial.sh`. Begin with the header as so (see
|
|
"Writing Tests" and "Source 'test-lib.sh'" in `t/README`):
|
|
|
|
----
|
|
#!/bin/sh
|
|
|
|
test_description='git-psuh test
|
|
|
|
This test runs git-psuh and makes sure it does not crash.'
|
|
|
|
. ./test-lib.sh
|
|
----
|
|
|
|
Tests are framed inside of a `test_expect_success` in order to output TAP
|
|
formatted results. Let's make sure that `git psuh` doesn't exit poorly and does
|
|
mention the right animal somewhere:
|
|
|
|
----
|
|
test_expect_success 'runs correctly with no args and good output' '
|
|
git psuh >actual &&
|
|
grep Pony actual
|
|
'
|
|
----
|
|
|
|
Indicate that you've run everything you wanted by adding the following at the
|
|
bottom of your script:
|
|
|
|
----
|
|
test_done
|
|
----
|
|
|
|
Make sure you mark your test script executable:
|
|
|
|
----
|
|
$ chmod +x t/t9999-psuh-tutorial.sh
|
|
----
|
|
|
|
You can get an idea of whether you created your new test script successfully
|
|
by running `make -C t test-lint`, which will check for things like test number
|
|
uniqueness, executable bit, and so on.
|
|
|
|
[[local-test]]
|
|
=== Running Locally
|
|
|
|
Let's try and run locally:
|
|
|
|
----
|
|
$ make
|
|
$ cd t/ && prove t9999-psuh-tutorial.sh
|
|
----
|
|
|
|
You can run the full test suite and ensure `git-psuh` didn't break anything:
|
|
|
|
----
|
|
$ cd t/
|
|
$ prove -j$(nproc) --shuffle t[0-9]*.sh
|
|
----
|
|
|
|
NOTE: You can also do this with `make test` or use any testing harness which can
|
|
speak TAP. `prove` can run concurrently. `shuffle` randomizes the order the
|
|
tests are run in, which makes them resilient against unwanted inter-test
|
|
dependencies. `prove` also makes the output nicer.
|
|
|
|
Go ahead and commit this change, as well.
|
|
|
|
[[ready-to-share]]
|
|
== Getting Ready to Share
|
|
|
|
You may have noticed already that the Git project performs its code reviews via
|
|
emailed patches, which are then applied by the maintainer when they are ready
|
|
and approved by the community. The Git project does not accept patches from
|
|
pull requests, and the patches emailed for review need to be formatted a
|
|
specific way. At this point the tutorial diverges, in order to demonstrate two
|
|
different methods of formatting your patchset and getting it reviewed.
|
|
|
|
The first method to be covered is GitGitGadget, which is useful for those
|
|
already familiar with GitHub's common pull request workflow. This method
|
|
requires a GitHub account.
|
|
|
|
The second method to be covered is `git send-email`, which can give slightly
|
|
more fine-grained control over the emails to be sent. This method requires some
|
|
setup which can change depending on your system and will not be covered in this
|
|
tutorial.
|
|
|
|
Regardless of which method you choose, your engagement with reviewers will be
|
|
the same; the review process will be covered after the sections on GitGitGadget
|
|
and `git send-email`.
|
|
|
|
[[howto-ggg]]
|
|
== Sending Patches via GitGitGadget
|
|
|
|
One option for sending patches is to follow a typical pull request workflow and
|
|
send your patches out via GitGitGadget. GitGitGadget is a tool created by
|
|
Johannes Schindelin to make life as a Git contributor easier for those used to
|
|
the GitHub PR workflow. It allows contributors to open pull requests against its
|
|
mirror of the Git project, and does some magic to turn the PR into a set of
|
|
emails and send them out for you. It also runs the Git continuous integration
|
|
suite for you. It's documented at http://gitgitgadget.github.io.
|
|
|
|
[[create-fork]]
|
|
=== Forking `git/git` on GitHub
|
|
|
|
Before you can send your patch off to be reviewed using GitGitGadget, you will
|
|
need to fork the Git project and upload your changes. First thing - make sure
|
|
you have a GitHub account.
|
|
|
|
Head to the https://github.com/git/git[GitHub mirror] and look for the Fork
|
|
button. Place your fork wherever you deem appropriate and create it.
|
|
|
|
[[upload-to-fork]]
|
|
=== Uploading to Your Own Fork
|
|
|
|
To upload your branch to your own fork, you'll need to add the new fork as a
|
|
remote. You can use `git remote -v` to show the remotes you have added already.
|
|
From your new fork's page on GitHub, you can press "Clone or download" to get
|
|
the URL; then you need to run the following to add, replacing your own URL and
|
|
remote name for the examples provided:
|
|
|
|
----
|
|
$ git remote add remotename git@github.com:remotename/git.git
|
|
----
|
|
|
|
or to use the HTTPS URL:
|
|
|
|
----
|
|
$ git remote add remotename https://github.com/remotename/git/.git
|
|
----
|
|
|
|
Run `git remote -v` again and you should see the new remote showing up.
|
|
`git fetch remotename` (with the real name of your remote replaced) in order to
|
|
get ready to push.
|
|
|
|
Next, double-check that you've been doing all your development in a new branch
|
|
by running `git branch`. If you didn't, now is a good time to move your new
|
|
commits to their own branch.
|
|
|
|
As mentioned briefly at the beginning of this document, we are basing our work
|
|
on `master`, so go ahead and update as shown below, or using your preferred
|
|
workflow.
|
|
|
|
----
|
|
$ git checkout master
|
|
$ git pull -r
|
|
$ git rebase master psuh
|
|
----
|
|
|
|
Finally, you're ready to push your new topic branch! (Due to our branch and
|
|
command name choices, be careful when you type the command below.)
|
|
|
|
----
|
|
$ git push remotename psuh
|
|
----
|
|
|
|
Now you should be able to go and check out your newly created branch on GitHub.
|
|
|
|
[[send-pr-ggg]]
|
|
=== Sending a PR to GitGitGadget
|
|
|
|
In order to have your code tested and formatted for review, you need to start by
|
|
opening a Pull Request against `gitgitgadget/git`. Head to
|
|
https://github.com/gitgitgadget/git and open a PR either with the "New pull
|
|
request" button or the convenient "Compare & pull request" button that may
|
|
appear with the name of your newly pushed branch.
|
|
|
|
Review the PR's title and description, as it's used by GitGitGadget as the cover
|
|
letter for your change. When you're happy, submit your pull request.
|
|
|
|
[[run-ci-ggg]]
|
|
=== Running CI and Getting Ready to Send
|
|
|
|
If it's your first time using GitGitGadget (which is likely, as you're using
|
|
this tutorial) then someone will need to give you permission to use the tool.
|
|
As mentioned in the GitGitGadget documentation, you just need someone who
|
|
already uses it to comment on your PR with `/allow <username>`. GitGitGadget
|
|
will automatically run your PRs through the CI even without the permission given
|
|
but you will not be able to `/submit` your changes until someone allows you to
|
|
use the tool.
|
|
|
|
NOTE: You can typically find someone who can `/allow` you on GitGitGadget by
|
|
either examining recent pull requests where someone has been granted `/allow`
|
|
(https://github.com/gitgitgadget/git/pulls?utf8=%E2%9C%93&q=is%3Apr+is%3Aopen+%22%2Fallow%22[Search:
|
|
is:pr is:open "/allow"]), in which case both the author and the person who
|
|
granted the `/allow` can now `/allow` you, or by inquiring on the
|
|
https://web.libera.chat/#git-devel[#git-devel] IRC channel on Libera Chat
|
|
linking your pull request and asking for someone to `/allow` you.
|
|
|
|
If the CI fails, you can update your changes with `git rebase -i` and push your
|
|
branch again:
|
|
|
|
----
|
|
$ git push -f remotename psuh
|
|
----
|
|
|
|
In fact, you should continue to make changes this way up until the point when
|
|
your patch is accepted into `next`.
|
|
|
|
////
|
|
TODO https://github.com/gitgitgadget/gitgitgadget/issues/83
|
|
It'd be nice to be able to verify that the patch looks good before sending it
|
|
to everyone on Git mailing list.
|
|
[[check-work-ggg]]
|
|
=== Check Your Work
|
|
////
|
|
|
|
[[send-mail-ggg]]
|
|
=== Sending Your Patches
|
|
|
|
Now that your CI is passing and someone has granted you permission to use
|
|
GitGitGadget with the `/allow` command, sending out for review is as simple as
|
|
commenting on your PR with `/submit`.
|
|
|
|
[[responding-ggg]]
|
|
=== Updating With Comments
|
|
|
|
Skip ahead to <<reviewing,Responding to Reviews>> for information on how to
|
|
reply to review comments you will receive on the mailing list.
|
|
|
|
Once you have your branch again in the shape you want following all review
|
|
comments, you can submit again:
|
|
|
|
----
|
|
$ git push -f remotename psuh
|
|
----
|
|
|
|
Next, go look at your pull request against GitGitGadget; you should see the CI
|
|
has been kicked off again. Now while the CI is running is a good time for you
|
|
to modify your description at the top of the pull request thread; it will be
|
|
used again as the cover letter. You should use this space to describe what
|
|
has changed since your previous version, so that your reviewers have some idea
|
|
of what they're looking at. When the CI is done running, you can comment once
|
|
more with `/submit` - GitGitGadget will automatically add a v2 mark to your
|
|
changes.
|
|
|
|
[[howto-git-send-email]]
|
|
== Sending Patches with `git send-email`
|
|
|
|
If you don't want to use GitGitGadget, you can also use Git itself to mail your
|
|
patches. Some benefits of using Git this way include finer grained control of
|
|
subject line (for example, being able to use the tag [RFC PATCH] in the subject)
|
|
and being able to send a ``dry run'' mail to yourself to ensure it all looks
|
|
good before going out to the list.
|
|
|
|
[[setup-git-send-email]]
|
|
=== Prerequisite: Setting Up `git send-email`
|
|
|
|
Configuration for `send-email` can vary based on your operating system and email
|
|
provider, and so will not be covered in this tutorial, beyond stating that in
|
|
many distributions of Linux, `git-send-email` is not packaged alongside the
|
|
typical `git` install. You may need to install this additional package; there
|
|
are a number of resources online to help you do so. You will also need to
|
|
determine the right way to configure it to use your SMTP server; again, as this
|
|
configuration can change significantly based on your system and email setup, it
|
|
is out of scope for the context of this tutorial.
|
|
|
|
[[format-patch]]
|
|
=== Preparing Initial Patchset
|
|
|
|
Sending emails with Git is a two-part process; before you can prepare the emails
|
|
themselves, you'll need to prepare the patches. Luckily, this is pretty simple:
|
|
|
|
----
|
|
$ git format-patch --cover-letter -o psuh/ --base=auto psuh@{u}..psuh
|
|
----
|
|
|
|
. The `--cover-letter` option tells `format-patch` to create a
|
|
cover letter template for you. You will need to fill in the
|
|
template before you're ready to send - but for now, the template
|
|
will be next to your other patches.
|
|
|
|
. The `-o psuh/` option tells `format-patch` to place the patch
|
|
files into a directory. This is useful because `git send-email`
|
|
can take a directory and send out all the patches from there.
|
|
|
|
. The `--base=auto` option tells the command to record the "base
|
|
commit", on which the recipient is expected to apply the patch
|
|
series. The `auto` value will cause `format-patch` to compute
|
|
the base commit automatically, which is the merge base of tip
|
|
commit of the remote-tracking branch and the specified revision
|
|
range.
|
|
|
|
. The `psuh@{u}..psuh` option tells `format-patch` to generate
|
|
patches for the commits you created on the `psuh` branch since it
|
|
forked from its upstream (which is `origin/master` if you
|
|
followed the example in the "Set up your workspace" section). If
|
|
you are already on the `psuh` branch, you can just say `@{u}`,
|
|
which means "commits on the current branch since it forked from
|
|
its upstream", which is the same thing.
|
|
|
|
The command will make one patch file per commit. After you
|
|
run, you can go have a look at each of the patches with your favorite text
|
|
editor and make sure everything looks alright; however, it's not recommended to
|
|
make code fixups via the patch file. It's a better idea to make the change the
|
|
normal way using `git rebase -i` or by adding a new commit than by modifying a
|
|
patch.
|
|
|
|
NOTE: Optionally, you can also use the `--rfc` flag to prefix your patch subject
|
|
with ``[RFC PATCH]'' instead of ``[PATCH]''. RFC stands for ``request for
|
|
comments'' and indicates that while your code isn't quite ready for submission,
|
|
you'd like to begin the code review process. This can also be used when your
|
|
patch is a proposal, but you aren't sure whether the community wants to solve
|
|
the problem with that approach or not - to conduct a sort of design review. You
|
|
may also see on the list patches marked ``WIP'' - this means they are incomplete
|
|
but want reviewers to look at what they have so far. You can add this flag with
|
|
`--subject-prefix=WIP`.
|
|
|
|
Check and make sure that your patches and cover letter template exist in the
|
|
directory you specified - you're nearly ready to send out your review!
|
|
|
|
[[cover-letter]]
|
|
=== Preparing Email
|
|
|
|
In addition to an email per patch, the Git community also expects your patches
|
|
to come with a cover letter, typically with a subject line [PATCH 0/x] (where
|
|
x is the number of patches you're sending). Since you invoked `format-patch`
|
|
with `--cover-letter`, you've already got a template ready. Open it up in your
|
|
favorite editor.
|
|
|
|
You should see a number of headers present already. Check that your `From:`
|
|
header is correct. Then modify your `Subject:` to something which succinctly
|
|
covers the purpose of your entire topic branch, for example:
|
|
|
|
----
|
|
Subject: [PATCH 0/7] adding the 'psuh' command
|
|
----
|
|
|
|
Make sure you retain the ``[PATCH 0/X]'' part; that's what indicates to the Git
|
|
community that this email is the beginning of a review, and many reviewers
|
|
filter their email for this type of flag.
|
|
|
|
You'll need to add some extra parameters when you invoke `git send-email` to add
|
|
the cover letter.
|
|
|
|
Next you'll have to fill out the body of your cover letter. This is an important
|
|
component of change submission as it explains to the community from a high level
|
|
what you're trying to do, and why, in a way that's more apparent than just
|
|
looking at your diff. Be sure to explain anything your diff doesn't make clear
|
|
on its own.
|
|
|
|
Here's an example body for `psuh`:
|
|
|
|
----
|
|
Our internal metrics indicate widespread interest in the command
|
|
git-psuh - that is, many users are trying to use it, but finding it is
|
|
unavailable, using some unknown workaround instead.
|
|
|
|
The following handful of patches add the psuh command and implement some
|
|
handy features on top of it.
|
|
|
|
This patchset is part of the MyFirstContribution tutorial and should not
|
|
be merged.
|
|
----
|
|
|
|
The template created by `git format-patch --cover-letter` includes a diffstat.
|
|
This gives reviewers a summary of what they're in for when reviewing your topic.
|
|
The one generated for `psuh` from the sample implementation looks like this:
|
|
|
|
----
|
|
Documentation/git-psuh.txt | 40 +++++++++++++++++++++
|
|
Makefile | 1 +
|
|
builtin.h | 1 +
|
|
builtin/psuh.c | 73 ++++++++++++++++++++++++++++++++++++++
|
|
git.c | 1 +
|
|
t/t9999-psuh-tutorial.sh | 12 +++++++
|
|
6 files changed, 128 insertions(+)
|
|
create mode 100644 Documentation/git-psuh.txt
|
|
create mode 100644 builtin/psuh.c
|
|
create mode 100755 t/t9999-psuh-tutorial.sh
|
|
----
|
|
|
|
Finally, the letter will include the version of Git used to generate the
|
|
patches. You can leave that string alone.
|
|
|
|
[[sending-git-send-email]]
|
|
=== Sending Email
|
|
|
|
At this point you should have a directory `psuh/` which is filled with your
|
|
patches and a cover letter. Time to mail it out! You can send it like this:
|
|
|
|
----
|
|
$ git send-email --to=target@example.com psuh/*.patch
|
|
----
|
|
|
|
NOTE: Check `git help send-email` for some other options which you may find
|
|
valuable, such as changing the Reply-to address or adding more CC and BCC lines.
|
|
|
|
NOTE: When you are sending a real patch, it will go to git@vger.kernel.org - but
|
|
please don't send your patchset from the tutorial to the real mailing list! For
|
|
now, you can send it to yourself, to make sure you understand how it will look.
|
|
|
|
After you run the command above, you will be presented with an interactive
|
|
prompt for each patch that's about to go out. This gives you one last chance to
|
|
edit or quit sending something (but again, don't edit code this way). Once you
|
|
press `y` or `a` at these prompts your emails will be sent! Congratulations!
|
|
|
|
Awesome, now the community will drop everything and review your changes. (Just
|
|
kidding - be patient!)
|
|
|
|
[[v2-git-send-email]]
|
|
=== Sending v2
|
|
|
|
This section will focus on how to send a v2 of your patchset. To learn what
|
|
should go into v2, skip ahead to <<reviewing,Responding to Reviews>> for
|
|
information on how to handle comments from reviewers.
|
|
|
|
We'll reuse our `psuh` topic branch for v2. Before we make any changes, we'll
|
|
mark the tip of our v1 branch for easy reference:
|
|
|
|
----
|
|
$ git checkout psuh
|
|
$ git branch psuh-v1
|
|
----
|
|
|
|
Refine your patch series by using `git rebase -i` to adjust commits based upon
|
|
reviewer comments. Once the patch series is ready for submission, generate your
|
|
patches again, but with some new flags:
|
|
|
|
----
|
|
$ git format-patch -v2 --cover-letter -o psuh/ --range-diff master..psuh-v1 master..
|
|
----
|
|
|
|
The `--range-diff master..psuh-v1` parameter tells `format-patch` to include a
|
|
range-diff between `psuh-v1` and `psuh` in the cover letter (see
|
|
linkgit:git-range-diff[1]). This helps tell reviewers about the differences
|
|
between your v1 and v2 patches.
|
|
|
|
The `-v2` parameter tells `format-patch` to output your patches
|
|
as version "2". For instance, you may notice that your v2 patches are
|
|
all named like `v2-000n-my-commit-subject.patch`. `-v2` will also format
|
|
your patches by prefixing them with "[PATCH v2]" instead of "[PATCH]",
|
|
and your range-diff will be prefaced with "Range-diff against v1".
|
|
|
|
Afer you run this command, `format-patch` will output the patches to the `psuh/`
|
|
directory, alongside the v1 patches. Using a single directory makes it easy to
|
|
refer to the old v1 patches while proofreading the v2 patches, but you will need
|
|
to be careful to send out only the v2 patches. We will use a pattern like
|
|
"psuh/v2-*.patch" (not "psuh/*.patch", which would match v1 and v2 patches).
|
|
|
|
Edit your cover letter again. Now is a good time to mention what's different
|
|
between your last version and now, if it's something significant. You do not
|
|
need the exact same body in your second cover letter; focus on explaining to
|
|
reviewers the changes you've made that may not be as visible.
|
|
|
|
You will also need to go and find the Message-Id of your previous cover letter.
|
|
You can either note it when you send the first series, from the output of `git
|
|
send-email`, or you can look it up on the
|
|
https://lore.kernel.org/git[mailing list]. Find your cover letter in the
|
|
archives, click on it, then click "permalink" or "raw" to reveal the Message-Id
|
|
header. It should match:
|
|
|
|
----
|
|
Message-Id: <foo.12345.author@example.com>
|
|
----
|
|
|
|
Your Message-Id is `<foo.12345.author@example.com>`. This example will be used
|
|
below as well; make sure to replace it with the correct Message-Id for your
|
|
**previous cover letter** - that is, if you're sending v2, use the Message-Id
|
|
from v1; if you're sending v3, use the Message-Id from v2.
|
|
|
|
While you're looking at the email, you should also note who is CC'd, as it's
|
|
common practice in the mailing list to keep all CCs on a thread. You can add
|
|
these CC lines directly to your cover letter with a line like so in the header
|
|
(before the Subject line):
|
|
|
|
----
|
|
CC: author@example.com, Othe R <other@example.com>
|
|
----
|
|
|
|
Now send the emails again, paying close attention to which messages you pass in
|
|
to the command:
|
|
|
|
----
|
|
$ git send-email --to=target@example.com
|
|
--in-reply-to="<foo.12345.author@example.com>"
|
|
psuh/v2-*.patch
|
|
----
|
|
|
|
[[single-patch]]
|
|
=== Bonus Chapter: One-Patch Changes
|
|
|
|
In some cases, your very small change may consist of only one patch. When that
|
|
happens, you only need to send one email. Your commit message should already be
|
|
meaningful and explain at a high level the purpose (what is happening and why)
|
|
of your patch, but if you need to supply even more context, you can do so below
|
|
the `---` in your patch. Take the example below, which was generated with `git
|
|
format-patch` on a single commit, and then edited to add the content between
|
|
the `---` and the diffstat.
|
|
|
|
----
|
|
From 1345bbb3f7ac74abde040c12e737204689a72723 Mon Sep 17 00:00:00 2001
|
|
From: A U Thor <author@example.com>
|
|
Date: Thu, 18 Apr 2019 15:11:02 -0700
|
|
Subject: [PATCH] README: change the grammar
|
|
|
|
I think it looks better this way. This part of the commit message will
|
|
end up in the commit-log.
|
|
|
|
Signed-off-by: A U Thor <author@example.com>
|
|
---
|
|
Let's have a wild discussion about grammar on the mailing list. This
|
|
part of my email will never end up in the commit log. Here is where I
|
|
can add additional context to the mailing list about my intent, outside
|
|
of the context of the commit log. This section was added after `git
|
|
format-patch` was run, by editing the patch file in a text editor.
|
|
|
|
README.md | 2 +-
|
|
1 file changed, 1 insertion(+), 1 deletion(-)
|
|
|
|
diff --git a/README.md b/README.md
|
|
index 88f126184c..38da593a60 100644
|
|
--- a/README.md
|
|
+++ b/README.md
|
|
@@ -3,7 +3,7 @@
|
|
Git - fast, scalable, distributed revision control system
|
|
=========================================================
|
|
|
|
-Git is a fast, scalable, distributed revision control system with an
|
|
+Git is a fast, scalable, and distributed revision control system with an
|
|
unusually rich command set that provides both high-level operations
|
|
and full access to internals.
|
|
|
|
--
|
|
2.21.0.392.gf8f6787159e-goog
|
|
----
|
|
|
|
[[now-what]]
|
|
== My Patch Got Emailed - Now What?
|
|
|
|
[[reviewing]]
|
|
=== Responding to Reviews
|
|
|
|
After a few days, you will hopefully receive a reply to your patchset with some
|
|
comments. Woohoo! Now you can get back to work.
|
|
|
|
It's good manners to reply to each comment, notifying the reviewer that you have
|
|
made the change suggested, feel the original is better, or that the comment
|
|
inspired you to do something a new way which is superior to both the original
|
|
and the suggested change. This way reviewers don't need to inspect your v2 to
|
|
figure out whether you implemented their comment or not.
|
|
|
|
Reviewers may ask you about what you wrote in the patchset, either in
|
|
the proposed commit log message or in the changes themselves. You
|
|
should answer these questions in your response messages, but often the
|
|
reason why reviewers asked these questions to understand what you meant
|
|
to write is because your patchset needed clarification to be understood.
|
|
|
|
Do not be satisfied by just answering their questions in your response
|
|
and hear them say that they now understand what you wanted to say.
|
|
Update your patches to clarify the points reviewers had trouble with,
|
|
and prepare your v2; the words you used to explain your v1 to answer
|
|
reviewers' questions may be useful thing to use. Your goal is to make
|
|
your v2 clear enough so that it becomes unnecessary for you to give the
|
|
same explanation to the next person who reads it.
|
|
|
|
If you are going to push back on a comment, be polite and explain why you feel
|
|
your original is better; be prepared that the reviewer may still disagree with
|
|
you, and the rest of the community may weigh in on one side or the other. As
|
|
with all code reviews, it's important to keep an open mind to doing something a
|
|
different way than you originally planned; other reviewers have a different
|
|
perspective on the project than you do, and may be thinking of a valid side
|
|
effect which had not occurred to you. It is always okay to ask for clarification
|
|
if you aren't sure why a change was suggested, or what the reviewer is asking
|
|
you to do.
|
|
|
|
Make sure your email client has a plaintext email mode and it is turned on; the
|
|
Git list rejects HTML email. Please also follow the mailing list etiquette
|
|
outlined in the
|
|
https://kernel.googlesource.com/pub/scm/git/git/+/todo/MaintNotes[Maintainer's
|
|
Note], which are similar to etiquette rules in most open source communities
|
|
surrounding bottom-posting and inline replies.
|
|
|
|
When you're making changes to your code, it is cleanest - that is, the resulting
|
|
commits are easiest to look at - if you use `git rebase -i` (interactive
|
|
rebase). Take a look at this
|
|
https://www.oreilly.com/library/view/git-pocket-guide/9781449327507/ch10.html[overview]
|
|
from O'Reilly. The general idea is to modify each commit which requires changes;
|
|
this way, instead of having a patch A with a mistake, a patch B which was fine
|
|
and required no upstream reviews in v1, and a patch C which fixes patch A for
|
|
v2, you can just ship a v2 with a correct patch A and correct patch B. This is
|
|
changing history, but since it's local history which you haven't shared with
|
|
anyone, that is okay for now! (Later, it may not make sense to do this; take a
|
|
look at the section below this one for some context.)
|
|
|
|
[[after-approval]]
|
|
=== After Review Approval
|
|
|
|
The Git project has four integration branches: `seen`, `next`, `master`, and
|
|
`maint`. Your change will be placed into `seen` fairly early on by the maintainer
|
|
while it is still in the review process; from there, when it is ready for wider
|
|
testing, it will be merged into `next`. Plenty of early testers use `next` and
|
|
may report issues. Eventually, changes in `next` will make it to `master`,
|
|
which is typically considered stable. Finally, when a new release is cut,
|
|
`maint` is used to base bugfixes onto. As mentioned at the beginning of this
|
|
document, you can read `Documents/SubmittingPatches` for some more info about
|
|
the use of the various integration branches.
|
|
|
|
Back to now: your code has been lauded by the upstream reviewers. It is perfect.
|
|
It is ready to be accepted. You don't need to do anything else; the maintainer
|
|
will merge your topic branch to `next` and life is good.
|
|
|
|
However, if you discover it isn't so perfect after this point, you may need to
|
|
take some special steps depending on where you are in the process.
|
|
|
|
If the maintainer has announced in the "What's cooking in git.git" email that
|
|
your topic is marked for `next` - that is, that they plan to merge it to `next`
|
|
but have not yet done so - you should send an email asking the maintainer to
|
|
wait a little longer: "I've sent v4 of my series and you marked it for `next`,
|
|
but I need to change this and that - please wait for v5 before you merge it."
|
|
|
|
If the topic has already been merged to `next`, rather than modifying your
|
|
patches with `git rebase -i`, you should make further changes incrementally -
|
|
that is, with another commit, based on top of the maintainer's topic branch as
|
|
detailed in https://github.com/gitster/git. Your work is still in the same topic
|
|
but is now incremental, rather than a wholesale rewrite of the topic branch.
|
|
|
|
The topic branches in the maintainer's GitHub are mirrored in GitGitGadget, so
|
|
if you're sending your reviews out that way, you should be sure to open your PR
|
|
against the appropriate GitGitGadget/Git branch.
|
|
|
|
If you're using `git send-email`, you can use it the same way as before, but you
|
|
should generate your diffs from `<topic>..<mybranch>` and base your work on
|
|
`<topic>` instead of `master`.
|