[PATCH v6 2/2] revision: implement `git log --merge` also for rebase/cherry-pick/revert
- From
Philippe Blain <levraiphilippeblain@gmail.com>
- Date
- Feb 28, 2024, 13:54 UTC
- Message-ID
- <20240228-ml-log-merge-with-cherry-pick-and-other-pseudo-heads-v6-2-8ec34c052b39@gmail.com>
- In-Reply-To
- <20240228-ml-log-merge-with-cherry-pick-and-other-pseudo-heads-v6-0-8ec34c052b39@gmail.com>
From: Michael Lohmann <mi.al.lohmann@gmail.com>
'git log' learned in ae3e5e1ef2 (git log -p --merge [[--] paths...], 2006-07-03) to show commits touching conflicted files in the range HEAD...MERGE_HEAD, an addition documented in d249b45547 (Document rev-list's option --merge, 2006-08-04).
It can be useful to look at the commit history to understand what lead to merge conflicts also for other mergy operations besides merges, like cherry-pick, revert and rebase.
For rebases and cherry-picks, an interesting range to look at is HEAD...{REBASE_HEAD,CHERRY_PICK_HEAD}, since even if all the commits included in that range are not directly part of the 3-way merge, conflicts encountered during these operations can indeed be caused by changes introduced in preceding commits on both sides of the history.
For revert, as we are (most likely) reversing changes from a previous commit, an appropriate range is REVERT_HEAD..HEAD, which is equivalent to REVERT_HEAD...HEAD and to HEAD...REVERT_HEAD, if we keep HEAD and its parents on the left side of the range.
As such, adjust the code in prepare_show_merge so it constructs the range HEAD...$OTHER for OTHER={MERGE_HEAD, CHERRY_PICK_HEAD, REVERT_HEAD or REBASE_HEAD}. Note that we try these pseudorefs in order, so keep REBASE_HEAD last since the three other operations can be performed during a rebase. Note also that in the uncommon case where $OTHER and HEAD do not share a common ancestor, this will show the complete histories of both sides since their root commits, which is the same behaviour as currently happens in that case for HEAD and MERGE_HEAD.
Adjust the documentation of this option accordingly.
Co-authored-by: Johannes Sixt <j6t@kdbg.org> Co-authored-by: Philippe Blain <levraiphilippeblain@gmail.com> Signed-off-by: Michael Lohmann <mi.al.lohmann@gmail.com> [jc: tweaked in j6t's precedence fix that tries REBASE_HEAD last] Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com> --- Documentation/rev-list-options.txt | 7 +++++-- revision.c | 31 +++++++++++++++++++++++-------- 2 files changed, 28 insertions(+), 10 deletions(-)
diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt index a583b52c61..29e7b50bcf 100644 --- a/Documentation/rev-list-options.txt +++ b/Documentation/rev-list-options.txt @@ -341,8 +341,11 @@ See also linkgit:git-reflog[1]. Under `--pretty=reference`, this information will not be shown at all. --merge:: - After a failed merge, show refs that touch files having a - conflict and don't exist on all heads to merge. + Show commits touching conflicted paths in the range `HEAD...<other>`, + where `<other>` is the first existing pseudoref in `MERGE_HEAD`, + `CHERRY_PICK_HEAD`, `REVERT_HEAD` or `REBASE_HEAD`. Only works + when the index has unmerged entries. This option can be used to show + relevant commits when resolving conflicts from a 3-way merge. --boundary:: Output excluded boundary commits. Boundary commits are diff --git a/revision.c b/revision.c index df775f74d0..d2ebdd045a 100644 --- a/revision.c +++ b/revision.c @@ -1961,11 +1961,31 @@ static void add_pending_commit_list(struct rev_info *revs, } } +static const char *lookup_other_head(struct object_id *oid) +{ + int i; + static const char *const other_head[] = { + "MERGE_HEAD", "CHERRY_PICK_HEAD", "REVERT_HEAD", "REBASE_HEAD" + }; + + for (i = 0; i < ARRAY_SIZE(other_head); i++) + if (!read_ref_full(other_head[i], + RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE, + oid, NULL)) { + if (is_null_oid(oid)) + die(_("%s exists but is a symbolic ref"), other_head[i]); + return other_head[i]; + } + + die(_("--merge requires one of the pseudorefs MERGE_HEAD, CHERRY_PICK_HEAD, REVERT_HEAD or REBASE_HEAD")); +} + static void prepare_show_merge(struct rev_info *revs) { struct commit_list *bases; struct commit *head, *other; struct object_id oid; + const char *other_name; const char **prune = NULL; int i, prune_num = 1; /* counting terminating NULL */ struct index_state *istate = revs->repo->index; @@ -1973,15 +1993,10 @@ static void prepare_show_merge(struct rev_info *revs) if (repo_get_oid(the_repository, "HEAD", &oid)) die("--merge without HEAD?"); head = lookup_commit_or_die(&oid, "HEAD"); - if (read_ref_full("MERGE_HEAD", - RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE, - &oid, NULL)) - die("--merge without MERGE_HEAD?"); - if (is_null_oid(&oid)) - die(_("MERGE_HEAD exists but is a symbolic ref")); - other = lookup_commit_or_die(&oid, "MERGE_HEAD"); + other_name = lookup_other_head(&oid); + other = lookup_commit_or_die(&oid, other_name); add_pending_object(revs, &head->object, "HEAD"); - add_pending_object(revs, &other->object, "MERGE_HEAD"); + add_pending_object(revs, &other->object, other_name); bases = repo_get_merge_bases(the_repository, head, other); add_rev_cmdline_list(revs, bases, REV_CMD_MERGE_BASE, UNINTERESTING | BOTTOM); add_pending_commit_list(revs, bases, UNINTERESTING | BOTTOM);
-- 2.39.1