From 32f7037ab31fa2dcf179bc07bf1cea2b732f6543 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Martin=20=C3=85gren?= Date: Mon, 25 May 2020 19:06:07 +0200 Subject: [PATCH] rev-list-options.txt: start a list for `show-pulls` MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The explanation of the `--show-pulls` option added in commit 8d049e182e ("revision: --show-pulls adds helpful merges", 2020-04-10) consists of several paragraphs and we use "+" throughout to tie them together in one long chain of list continuations. Only thing is, we're not in any kind of list, so these pluses end up being rendered literally. The preceding few paragraphs describe `--ancestry-path` and there we *do* have a list, since we've started one with `--ancestry-path::`. In fact, we have several such lists for all the various history-simplifying options we're discussing earlier in this file. Thus, we're missing a list both from a consistency point of view and from a practical rendering standpoint. Let's start a list for `--show-pulls` where we start actually discussing the option, and keep the paragraphs preceding it out of that list. That is, drop all those pluses before the new list we're adding here. Helped-by: Derrick Stolee Signed-off-by: Martin Ågren Reviewed-by: Derrick Stolee Signed-off-by: Junio C Hamano --- Documentation/rev-list-options.txt | 35 ++++++++++++++++-------------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt index 04ad7dd36e..b01b2b6773 100644 --- a/Documentation/rev-list-options.txt +++ b/Documentation/rev-list-options.txt @@ -581,12 +581,12 @@ option does. Applied to the 'D..M' range, it results in: Before discussing another option, `--show-pulls`, we need to create a new example history. -+ + A common problem users face when looking at simplified history is that a commit they know changed a file somehow does not appear in the file's simplified history. Let's demonstrate a new example and show how options such as `--full-history` and `--simplify-merges` works in that case: -+ + ----------------------------------------------------------------------- .-A---M-----C--N---O---P / / \ \ \/ / / @@ -595,7 +595,7 @@ such as `--full-history` and `--simplify-merges` works in that case: \ / /\ / `---X--' `---Y--' ----------------------------------------------------------------------- -+ + For this example, suppose `I` created `file.txt` which was modified by `A`, `B`, and `X` in different ways. The single-parent commits `C`, `Z`, and `Y` do not change `file.txt`. The merge commit `M` was created by @@ -607,19 +607,19 @@ the contents of `file.txt` at `X`. Hence, `R` is TREESAME to `X` but not contents of `file.txt` at `R`, so `N` is TREESAME to `R` but not `C`. The merge commits `O` and `P` are TREESAME to their first parents, but not to their second parents, `Z` and `Y` respectively. -+ + When using the default mode, `N` and `R` both have a TREESAME parent, so those edges are walked and the others are ignored. The resulting history graph is: -+ + ----------------------------------------------------------------------- I---X ----------------------------------------------------------------------- -+ + When using `--full-history`, Git walks every edge. This will discover the commits `A` and `B` and the merge `M`, but also will reveal the merge commits `O` and `P`. With parent rewriting, the resulting graph is: -+ + ----------------------------------------------------------------------- .-A---M--------N---O---P / / \ \ \/ / / @@ -628,21 +628,21 @@ merge commits `O` and `P`. With parent rewriting, the resulting graph is: \ / /\ / `---X--' `------' ----------------------------------------------------------------------- -+ + Here, the merge commits `O` and `P` contribute extra noise, as they did not actually contribute a change to `file.txt`. They only merged a topic that was based on an older version of `file.txt`. This is a common issue in repositories using a workflow where many contributors work in parallel and merge their topic branches along a single trunk: manu unrelated merges appear in the `--full-history` results. -+ + When using the `--simplify-merges` option, the commits `O` and `P` disappear from the results. This is because the rewritten second parents of `O` and `P` are reachable from their first parents. Those edges are removed and then the commits look like single-parent commits that are TREESAME to their parent. This also happens to the commit `N`, resulting in a history view as follows: -+ + ----------------------------------------------------------------------- .-A---M--. / / \ @@ -651,18 +651,18 @@ in a history view as follows: \ / / `---X--' ----------------------------------------------------------------------- -+ + In this view, we see all of the important single-parent changes from `A`, `B`, and `X`. We also see the carefully-resolved merge `M` and the not-so-carefully-resolved merge `R`. This is usually enough information to determine why the commits `A` and `B` "disappeared" from history in the default view. However, there are a few issues with this approach. -+ + The first issue is performance. Unlike any previous option, the `--simplify-merges` option requires walking the entire commit history before returning a single result. This can make the option difficult to use for very large repositories. -+ + The second issue is one of auditing. When many contributors are working on the same repository, it is important which merge commits introduced a change into an important branch. The problematic merge `R` above is @@ -671,10 +671,13 @@ important branch. Instead, the merge `N` was used to merge `R` and `X` into the important branch. This commit may have information about why the change `X` came to override the changes from `A` and `B` in its commit message. + +--show-pulls:: + In addition to the commits shown in the default history, show + each merge commit that is not TREESAME to its first parent but + is TREESAME to a later parent. + -The `--show-pulls` option helps with both of these issues by adding more -merge commits to the history results. If a merge is not TREESAME to its -first parent but is TREESAME to a later parent, then that merge is +When a merge commit is included by `--show-pulls`, the merge is treated as if it "pulled" the change from another branch. When using `--show-pulls` on this example (and no other options) the resulting graph is: