@matheusbsbs / matheus-bagliano / commits / f3fc5d9c91

revision: implement `git log --merge` also for rebase/cherry-pick/revert

'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> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Michael Lohmann committed Feb 28, 2024 at 08:54 UTC f3fc5d9c912df0e07c43a79f289220434f72b617
2 files changed +28 -10
Documentation/rev-list-options.txt
+5 -2
@@ -341,8 +341,11 @@ See also linkgit:git-reflog[1].
341 Under `--pretty=reference`, this information will not be shown at all.
342
343 --merge::
344 - After a failed merge, show refs that touch files having a
345 - conflict and don't exist on all heads to merge.
344 + Show commits touching conflicted paths in the range `HEAD...<other>`,
345 + where `<other>` is the first existing pseudoref in `MERGE_HEAD`,
346 + `CHERRY_PICK_HEAD`, `REVERT_HEAD` or `REBASE_HEAD`. Only works
347 + when the index has unmerged entries. This option can be used to show
348 + relevant commits when resolving conflicts from a 3-way merge.
349
350 --boundary::
351 Output excluded boundary commits. Boundary commits are
revision.c
+23 -8
@@ -1961,11 +1961,31 @@ static void add_pending_commit_list(struct rev_info *revs,
1961 }
1962 }
1963
1964 +static const char *lookup_other_head(struct object_id *oid)
1965 +{
1966 + int i;
1967 + static const char *const other_head[] = {
1968 + "MERGE_HEAD", "CHERRY_PICK_HEAD", "REVERT_HEAD", "REBASE_HEAD"
1969 + };
1970 +
1971 + for (i = 0; i < ARRAY_SIZE(other_head); i++)
1972 + if (!read_ref_full(other_head[i],
1973 + RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1974 + oid, NULL)) {
1975 + if (is_null_oid(oid))
1976 + die(_("%s exists but is a symbolic ref"), other_head[i]);
1977 + return other_head[i];
1978 + }
1979 +
1980 + die(_("--merge requires one of the pseudorefs MERGE_HEAD, CHERRY_PICK_HEAD, REVERT_HEAD or REBASE_HEAD"));
1981 +}
1982 +
1983 static void prepare_show_merge(struct rev_info *revs)
1984 {
1985 struct commit_list *bases;
1986 struct commit *head, *other;
1987 struct object_id oid;
1988 + const char *other_name;
1989 const char **prune = NULL;
1990 int i, prune_num = 1; /* counting terminating NULL */
1991 struct index_state *istate = revs->repo->index;
@@ -1973,15 +1993,10 @@ static void prepare_show_merge(struct rev_info *revs)
1993 if (repo_get_oid(the_repository, "HEAD", &oid))
1994 die("--merge without HEAD?");
1995 head = lookup_commit_or_die(&oid, "HEAD");
1976 - if (read_ref_full("MERGE_HEAD",
1977 - RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1978 - &oid, NULL))
1979 - die("--merge without MERGE_HEAD?");
1980 - if (is_null_oid(&oid))
1981 - die(_("MERGE_HEAD exists but is a symbolic ref"));
1982 - other = lookup_commit_or_die(&oid, "MERGE_HEAD");
1996 + other_name = lookup_other_head(&oid);
1997 + other = lookup_commit_or_die(&oid, other_name);
1998 add_pending_object(revs, &head->object, "HEAD");
1984 - add_pending_object(revs, &other->object, "MERGE_HEAD");
1999 + add_pending_object(revs, &other->object, other_name);
2000 bases = repo_get_merge_bases(the_repository, head, other);
2001 add_rev_cmdline_list(revs, bases, REV_CMD_MERGE_BASE, UNINTERESTING | BOTTOM);
2002 add_pending_commit_list(revs, bases, UNINTERESTING | BOTTOM);