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![Jeff King](/assets/img/avatar_default.png)
The point of these sections is generally to: 1. Give credit where it is due. 2. Give the reader an idea of where to ask questions or file bug reports. But they don't do a good job of either case. For (1), they are out of date and incomplete. A much more accurate answer can be gotten through shortlog or blame. For (2), the correct contact point is generally git@vger, and even if you wanted to cc the contact point, the out-of-date and incomplete fields mean you're likely sending to somebody useless. So let's drop the fields entirely from all manpages except git(1) itself. We already point people to the mailing list for bug reports there, and we can update the Authors section to give credit to the major contributors and point to shortlog and blame for more information. Each page has a "This is part of git" footer, so people can follow that to the main git manpage.
122 lines
4.5 KiB
Plaintext
122 lines
4.5 KiB
Plaintext
git-diff-index(1)
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=================
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NAME
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----
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git-diff-index - Compares content and mode of blobs between the index and repository
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SYNOPSIS
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--------
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'git diff-index' [-m] [--cached] [<common diff options>] <tree-ish> [<path>...]
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DESCRIPTION
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-----------
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Compares the content and mode of the blobs found via a tree
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object with the content of the current index and, optionally
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ignoring the stat state of the file on disk. When paths are
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specified, compares only those named paths. Otherwise all
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entries in the index are compared.
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OPTIONS
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-------
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include::diff-options.txt[]
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<tree-ish>::
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The id of a tree object to diff against.
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--cached::
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do not consider the on-disk file at all
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-m::
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By default, files recorded in the index but not checked
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out are reported as deleted. This flag makes
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'git diff-index' say that all non-checked-out files are up
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to date.
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include::diff-format.txt[]
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Operating Modes
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---------------
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You can choose whether you want to trust the index file entirely
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(using the '--cached' flag) or ask the diff logic to show any files
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that don't match the stat state as being "tentatively changed". Both
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of these operations are very useful indeed.
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Cached Mode
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-----------
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If '--cached' is specified, it allows you to ask:
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show me the differences between HEAD and the current index
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contents (the ones I'd write using 'git write-tree')
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For example, let's say that you have worked on your working directory, updated
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some files in the index and are ready to commit. You want to see exactly
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*what* you are going to commit, without having to write a new tree
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object and compare it that way, and to do that, you just do
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git diff-index --cached HEAD
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Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had
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done an `update-index` to make that effective in the index file.
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`git diff-files` wouldn't show anything at all, since the index file
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matches my working directory. But doing a 'git diff-index' does:
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torvalds@ppc970:~/git> git diff-index --cached HEAD
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-100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c
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+100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c
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You can see easily that the above is a rename.
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In fact, `git diff-index --cached` *should* always be entirely equivalent to
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actually doing a 'git write-tree' and comparing that. Except this one is much
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nicer for the case where you just want to check where you are.
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So doing a `git diff-index --cached` is basically very useful when you are
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asking yourself "what have I already marked for being committed, and
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what's the difference to a previous tree".
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Non-cached Mode
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---------------
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The "non-cached" mode takes a different approach, and is potentially
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the more useful of the two in that what it does can't be emulated with
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a 'git write-tree' + 'git diff-tree'. Thus that's the default mode.
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The non-cached version asks the question:
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show me the differences between HEAD and the currently checked out
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tree - index contents _and_ files that aren't up-to-date
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which is obviously a very useful question too, since that tells you what
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you *could* commit. Again, the output matches the 'git diff-tree -r'
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output to a tee, but with a twist.
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The twist is that if some file doesn't match the index, we don't have
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a backing store thing for it, and we use the magic "all-zero" sha1 to
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show that. So let's say that you have edited `kernel/sched.c`, but
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have not actually done a 'git update-index' on it yet - there is no
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"object" associated with the new state, and you get:
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torvalds@ppc970:~/v2.6/linux> git diff-index HEAD
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*100644->100664 blob 7476bb......->000000...... kernel/sched.c
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i.e., it shows that the tree has changed, and that `kernel/sched.c` has is
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not up-to-date and may contain new stuff. The all-zero sha1 means that to
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get the real diff, you need to look at the object in the working directory
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directly rather than do an object-to-object diff.
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NOTE: As with other commands of this type, 'git diff-index' does not
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actually look at the contents of the file at all. So maybe
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`kernel/sched.c` hasn't actually changed, and it's just that you
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touched it. In either case, it's a note that you need to
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'git update-index' it to make the index be in sync.
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NOTE: You can have a mixture of files show up as "has been updated"
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and "is still dirty in the working directory" together. You can always
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tell which file is in which state, since the "has been updated" ones
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show a valid sha1, and the "not in sync with the index" ones will
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always have the special all-zero sha1.
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GIT
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---
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Part of the linkgit:git[1] suite
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