Re: [PATCH 4/5] Documentation: document AUTO_MERGE

>
> From: Philippe Blain <levraiphilippeblain@gmail.com>
>
> Since 5291828df8 (merge-ort: write $GIT_DIR/AUTO_MERGE whenever we hit a
> conflict, 2021-03-20), when using the 'ort' merge strategy, the special
> ref AUTO_MERGE is written when a merge operation results in conflicts.
> This ref points to a tree recording the conflicted state of the working
> tree and is very useful during conflict resolution. However, this ref is
> not documented.
>
> Add some documentation for AUTO_MERGE in git-diff(1), git-merge(1),
> gitrevisions(7) and in the user manual.
>
> In git-diff(1), mention it at the end of the description section, when
> we mention that the command also accepts trees instead of commits, and
> also add an invocation to the "Various ways to check your working tree"
> example.
>
> In git-merge(1), add a step to the list of things that happen "when it
> is not obvious how to reconcile the changes", under the "True merge"
> secion. Also mention AUTO_MERGE in the "How to resolve conflicts"

> section, when mentioning 'git diff'.
>
> In gitrevisions(7), add a mention of AUTO_MERGE along with the other
> special refs.
>
> In the user manual, add a paragraph describing AUTO_MERGE to the
> "Getting conflict-resolution help during a merge" section, and include
> an example of a 'git diff AUTO_MERGE' invocation for the example
> conflict used in that section. Note that for uniformity we do not use
> backticks around AUTO_MERGE here since the rest of the document does not
> typeset special refs differently.
>
> Closes: https://github.com/gitgitgadget/git/issues/1471
> Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
> ---
>  Documentation/git-diff.txt    |  8 +++++++-
>  Documentation/git-merge.txt   |  9 +++++++--
>  Documentation/revisions.txt   |  6 +++++-
>  Documentation/user-manual.txt | 27 +++++++++++++++++++++++++++
>  4 files changed, 46 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/git-diff.txt b/Documentation/git-diff.txt
> index 52b679256c4..a85cc756ebc 100644
> --- a/Documentation/git-diff.txt
> +++ b/Documentation/git-diff.txt
> @@ -102,7 +102,11 @@ If --merge-base is given, use the merge base of the two commits for the
>  Just in case you are doing something exotic, it should be
>  noted that all of the <commit> in the above description, except
>  in the `--merge-base` case and in the last two forms that use `..`
> -notations, can be any <tree>.
> +notations, can be any <tree>. A tree of interest is the one pointed to
> +by the special ref `AUTO_MERGE`, which is written by the 'ort' merge
> +strategy upon hitting merge conflicts (see linkgit:git-merge[1]).
> +Comparing the working tree with `AUTO_MERGE` shows changes you've made
> +so far to resolve conflicts (see the examples below).
>
>  For a more complete list of ways to spell <commit>, see
>  "SPECIFYING REVISIONS" section in linkgit:gitrevisions[7].
> @@ -152,6 +156,7 @@ Various ways to check your working tree::
>  $ git diff            <1>
>  $ git diff --cached   <2>
>  $ git diff HEAD       <3>
> +$ git diff AUTO_MERGE <4>
>  ------------
>  +
>  <1> Changes in the working tree not yet staged for the next commit.
> @@ -159,6 +164,7 @@ $ git diff HEAD       <3>
>      would be committing if you run `git commit` without `-a` option.
>  <3> Changes in the working tree since your last commit; what you
>      would be committing if you run `git commit -a`
> +<4> Changes in the working tree you've made to resolve conflicts so far.
>
>  Comparing with arbitrary commits::
>  +
> diff --git a/Documentation/git-merge.txt b/Documentation/git-merge.txt
> index 23aefe28851..3f61389c1c2 100644
> --- a/Documentation/git-merge.txt
> +++ b/Documentation/git-merge.txt
> @@ -196,7 +196,11 @@ happens:
>     can inspect the stages with `git ls-files -u`).  The working
>     tree files contain the result of the merge operation; i.e. 3-way
>     merge results with familiar conflict markers `<<<` `===` `>>>`.
> -5. No other changes are made.  In particular, the local
> +5. A special ref `AUTO_MERGE` is written, pointing to a tree corresponding
> +   to the current content of the working tree (including conflict markers).
> +   Note that this ref is only written when the 'ort' merge strategy
> +   is used (the default).
> +6. No other changes are made.  In particular, the local
>     modifications you had before you started merge will stay the
>     same and the index entries for them stay as they were,
>     i.e. matching `HEAD`.
> @@ -336,7 +340,8 @@ You can work through the conflict with a number of tools:
>
>   * Look at the diffs.  `git diff` will show a three-way diff,
>     highlighting changes from both the `HEAD` and `MERGE_HEAD`
> -   versions.
> +   versions. `git diff AUTO_MERGE` will show what changes you've
> +   made so far to resolve conlicts.

>
>   * Look at the diffs from each branch. `git log --merge -p <path>`
>     will show diffs first for the `HEAD` version and then the
> diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt
> index 98b8f89bc8d..b42a2bb30a5 100644
> --- a/Documentation/revisions.txt
> +++ b/Documentation/revisions.txt
> @@ -33,7 +33,8 @@ characters and to avoid word splitting.
>
>    . If '$GIT_DIR/<refname>' exists, that is what you mean (this is usually
>      useful only for `HEAD`, `FETCH_HEAD`, `ORIG_HEAD`, `MERGE_HEAD`,
> -    `REBASE_HEAD`, `REVERT_HEAD`, `CHERRY_PICK_HEAD` and `BISECT_HEAD`);
> +    `REBASE_HEAD`, `REVERT_HEAD`, `CHERRY_PICK_HEAD`, `BISECT_HEAD`
> +    and `AUTO_MERGE`);
>
>    . otherwise, 'refs/<refname>' if it exists;
>
> @@ -64,6 +65,9 @@ run `git revert`.
>  when you run `git cherry-pick`.
>  `BISECT_HEAD` records the current commit to be tested when you
>  run `git bisect --no-checkout`.
> +`AUTO_MERGE` records a tree object corresponding to the state the
> +'ort' merge strategy wrote to the working tree when a merge operation
> +resulted in conflicts.
>  +
>  Note that any of the 'refs/*' cases above may come either from
>  the `$GIT_DIR/refs` directory or from the `$GIT_DIR/packed-refs` file.
> diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt
> index dc9c6a663a9..99e5f652e92 100644
> --- a/Documentation/user-manual.txt
> +++ b/Documentation/user-manual.txt
> @@ -1343,6 +1343,33 @@ $ git diff -3 file.txt           # diff against stage 3
>  $ git diff --theirs file.txt   # same as the above.
>  -------------------------------------------------
>
> +When using the 'ort' merge strategy (the default), before updating the working
> +tree with the result of the merge, Git writes a special ref named AUTO_MERGE
> +reflecting the state of the tree it is about to write. Conflicted paths that
> +could not be automatically merged are written to this tree with conflict
> +markers, just as in the working tree. AUTO_MERGE can thus be used with
> +linkgit:git-diff[1] to show the changes you've made so far to resolve
> +conflicts. Using the same example as above, after resolving the conflict we
> +get:

> +
> +-------------------------------------------------
> +$ git diff AUTO_MERGE
> +diff --git a/file.txt b/file.txt
> +index cd10406..8bf5ae7 100644
> +--- a/file.txt
> ++++ b/file.txt
> +@@ -1,5 +1 @@
> +-<<<<<<< HEAD:file.txt
> +-Hello world
> +-=======
> +-Goodbye
> +->>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
> ++Goodbye world
> +-------------------------------------------------
> +
> +Notice that the diff shows we deleted the conflict markers and both versions,
> +and wrote "Goodbye world" instead.
> +
>  The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help
>  for merges:
>
> --
> gitgitgadget
>