[PATCH v3 3/3] replay: allow to specify a ref with option --ref

[Toon Claes <toon@iotcl.com>]

When option '--onto' is passed to git-replay(1), the command will update
refs from the <revision-range> passed to the command. When using option
'--advance' or '--revert', the argument of that option is a ref that
will be updated.

To enable users to specify which ref to update, add option '--ref'. When
using option '--ref', the refs described above are left untouched and
instead the argument of this option is updated instead.

Because this introduces code paths in replay.c that jump to `out` before
init_basic_merge_options() is called on `merge_opt`, zero-initialize the
struct.

Signed-off-by: Toon Claes <toon@iotcl.com>
---
 Documentation/git-replay.adoc | 22 ++++++++++++++-
 builtin/replay.c              |  8 +++++-
 replay.c                      | 35 +++++++++++++++++------
 replay.h                      |  7 +++++
 t/t3650-replay-basics.sh      | 66 +++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 128 insertions(+), 10 deletions(-)

diff --git a/Documentation/git-replay.adoc b/Documentation/git-replay.adoc
index 5bb478c281..a32f72aead 100644
--- a/Documentation/git-replay.adoc
+++ b/Documentation/git-replay.adoc
@@ -10,7 +10,7 @@ SYNOPSIS
 --------
 [verse]
 (EXPERIMENTAL!) 'git replay' ([--contained] --onto=<newbase> | --advance=<branch> | --revert=<branch>)
-			     [--ref-action=<mode>] <revision-range>
+			     [--ref=<ref>] [--ref-action=<mode>] <revision-range>
 
 DESCRIPTION
 -----------
@@ -66,6 +66,16 @@ incompatible with `--contained` (which is a modifier for `--onto` only).
 	Update all branches that point at commits in
 	<revision-range>. Requires `--onto`.
 
+--ref=<ref>::
+	Override which reference is updated with the result of the replay.
+	The ref must be fully qualified.
+	When used with `--onto`, the `<revision-range>` should have a
+	single tip and only the specified reference is updated instead of
+	inferring refs from the revision range.
+	When used with `--advance` or `--revert`, the specified reference is
+	updated instead of the branch given to those options.
+	This option is incompatible with `--contained`.
+
 --ref-action[=<mode>]::
 	Control how references are updated. The mode can be:
 +
@@ -189,6 +199,16 @@ NOTE: For reverting an entire merge request as a single commit (rather than
 commit-by-commit), consider using `git merge-tree --merge-base $TIP HEAD $BASE`
 which can avoid unnecessary merge conflicts.
 
+To replay onto a specific commit while updating a different reference:
+
+------------
+$ git replay --onto=112233 --ref=refs/heads/mybranch aabbcc..ddeeff
+------------
+
+This replays the range `aabbcc..ddeeff` onto commit `112233` and updates
+`refs/heads/mybranch` to point at the result. This can be useful when you want
+to use bare commit IDs instead of branch names.
+
 GIT
 ---
 Part of the linkgit:git[1] suite
diff --git a/builtin/replay.c b/builtin/replay.c
index fbfeb780b6..39e3a86f6c 100644
--- a/builtin/replay.c
+++ b/builtin/replay.c
@@ -85,7 +85,7 @@ int cmd_replay(int argc,
 	const char *const replay_usage[] = {
 		N_("(EXPERIMENTAL!) git replay "
 		   "([--contained] --onto=<newbase> | --advance=<branch> | --revert=<branch>)\n"
-		   "[--ref-action=<mode>] <revision-range>"),
+		   "[--ref=<ref>] [--ref-action=<mode>] <revision-range>"),
 		NULL
 	};
 	struct option replay_options[] = {
@@ -103,6 +103,10 @@ int cmd_replay(int argc,
 			     N_("branch"),
 			     N_("revert commits onto given branch"),
 			     PARSE_OPT_NONEG),
+		OPT_STRING_F(0, "ref", &opts.ref,
+			     N_("branch"),
+			     N_("reference to update with result"),
+			     PARSE_OPT_NONEG),
 		OPT_STRING_F(0, "ref-action", &ref_action,
 			     N_("mode"),
 			     N_("control ref update behavior (update|print)"),
@@ -126,6 +130,8 @@ int cmd_replay(int argc,
 				  opts.contained, "--contained");
 	die_for_incompatible_opt2(!!opts.revert, "--revert",
 				  opts.contained, "--contained");
+	die_for_incompatible_opt2(!!opts.ref, "--ref",
+				  !!opts.contained, "--contained");
 
 	/* Parse ref action mode from command line or config */
 	ref_mode = get_ref_action_mode(repo, ref_action);
diff --git a/replay.c b/replay.c
index 199066f6b3..444f7ceefc 100644
--- a/replay.c
+++ b/replay.c
@@ -341,13 +341,15 @@ int replay_revisions(struct rev_info *revs,
 	struct commit *last_commit = NULL;
 	struct commit *commit;
 	struct commit *onto = NULL;
-	struct merge_options merge_opt;
+	struct merge_options merge_opt = { 0 };
 	struct merge_result result = {
 		.clean = 1,
 	};
 	bool detached_head;
 	char *advance;
 	char *revert;
+	const char *ref;
+	struct object_id old_oid;
 	enum replay_mode mode = REPLAY_MODE_PICK;
 	int ret;
 
@@ -358,6 +360,27 @@ int replay_revisions(struct rev_info *revs,
 	set_up_replay_mode(revs->repo, &revs->cmdline, opts->onto,
 			   &detached_head, &advance, &revert, &onto, &update_refs);
 
+	if (opts->ref) {
+		struct object_id oid;
+
+		if (update_refs && strset_get_size(update_refs) > 1) {
+			ret = error(_("'--ref' cannot be used with multiple revision ranges"));
+			goto out;
+		}
+		if (check_refname_format(opts->ref, 0) || !starts_with(opts->ref, "refs/")) {
+			ret = error(_("'%s' is not a valid refname"), opts->ref);
+			goto out;
+		}
+		ref = opts->ref;
+		if (!refs_read_ref(get_main_ref_store(revs->repo), opts->ref, &oid))
+			oidcpy(&old_oid, &oid);
+		else
+			oidclr(&old_oid, revs->repo->hash_algo);
+	} else {
+		ref = advance ? advance : revert;
+		oidcpy(&old_oid, &onto->object.oid);
+	}
+
 	/* FIXME: Should allow replaying commits with the first as a root commit */
 
 	if (prepare_revision_walk(revs) < 0) {
@@ -393,7 +416,7 @@ int replay_revisions(struct rev_info *revs,
 		kh_value(replayed_commits, pos) = last_commit;
 
 		/* Update any necessary branches */
-		if (advance || revert)
+		if (ref)
 			continue;
 
 		for (decoration = get_name_decoration(&commit->object);
@@ -427,13 +450,9 @@ int replay_revisions(struct rev_info *revs,
 		goto out;
 	}
 
-	/* In --advance or --revert mode, update the target ref */
-	if (advance || revert) {
-		const char *ref = advance ? advance : revert;
-		replay_result_queue_update(out, ref,
-					   &onto->object.oid,
+	if (ref)
+		replay_result_queue_update(out, ref, &old_oid,
 					   &last_commit->object.oid);
-	}
 
 	ret = 0;
 
diff --git a/replay.h b/replay.h
index e916a5f975..0ab74b9805 100644
--- a/replay.h
+++ b/replay.h
@@ -24,6 +24,13 @@ struct replay_revisions_options {
 	 */
 	const char *onto;
 
+	/*
+	 * Reference to update with the result of the replay. This will not
+	 * update any refs from `onto`, `advance`, or `revert`. Ignores
+	 * `contained`.
+	 */
+	const char *ref;
+
 	/*
 	 * Starting point at which to create revert commits; must be a branch
 	 * name. The branch will be updated to point to the revert commits.
diff --git a/t/t3650-replay-basics.sh b/t/t3650-replay-basics.sh
index 217f6fb292..d5c7dd1bf4 100755
--- a/t/t3650-replay-basics.sh
+++ b/t/t3650-replay-basics.sh
@@ -495,4 +495,70 @@ test_expect_success 'git replay --revert incompatible with --advance' '
 	test_grep "cannot be used together" error
 '
 
+test_expect_success 'using --onto with --ref' '
+	git branch test-ref-onto topic2 &&
+	test_when_finished "git branch -D test-ref-onto" &&
+
+	git replay --ref-action=print --onto=main --ref=refs/heads/test-ref-onto topic1..topic2 >result &&
+
+	test_line_count = 1 result &&
+	test_grep "^update refs/heads/test-ref-onto " result &&
+
+	git log --format=%s $(cut -f 3 -d " " result) >actual &&
+	test_write_lines E D M L B A >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'using --advance with --ref' '
+	git branch test-ref-advance main &&
+	git branch test-ref-target main &&
+	test_when_finished "git branch -D test-ref-advance test-ref-target" &&
+
+	git replay --ref-action=print --advance=test-ref-advance --ref=refs/heads/test-ref-target topic1..topic2 >result &&
+
+	test_line_count = 1 result &&
+	test_grep "^update refs/heads/test-ref-target " result
+'
+
+test_expect_success 'using --revert with --ref' '
+	git branch test-ref-revert topic4 &&
+	git branch test-ref-revert-target topic4 &&
+	test_when_finished "git branch -D test-ref-revert test-ref-revert-target" &&
+
+	git replay --ref-action=print --revert=test-ref-revert --ref=refs/heads/test-ref-revert-target topic4~1..topic4 >result &&
+
+	test_line_count = 1 result &&
+	test_grep "^update refs/heads/test-ref-revert-target " result
+'
+
+test_expect_success '--ref is incompatible with --contained' '
+	test_must_fail git replay --onto=main --ref=refs/heads/main --contained topic1..topic2 2>err &&
+	test_grep "cannot be used together" err
+'
+
+test_expect_success '--ref with nonexistent fully-qualified ref' '
+	test_when_finished "git update-ref -d refs/heads/new-branch" &&
+
+	git replay --onto=main --ref=refs/heads/new-branch topic1..topic2 &&
+
+	git log --format=%s -2 new-branch >actual &&
+	test_write_lines E D >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '--ref must be a valid refname' '
+	test_must_fail git replay --onto=main --ref="refs/heads/bad..ref" topic1..topic2 2>err &&
+	test_grep "is not a valid refname" err
+'
+
+test_expect_success '--ref requires fully qualified ref' '
+	test_must_fail git replay --onto=main --ref=main topic1..topic2 2>err &&
+	test_grep "is not a valid refname" err
+'
+
+test_expect_success '--onto with --ref rejects multiple revision ranges' '
+	test_must_fail git replay --onto=main --ref=refs/heads/topic2 ^topic1 topic2 topic4 2>err &&
+	test_grep "cannot be used with multiple revision ranges" err
+'
+
 test_done

-- 
2.53.0.310.g728cabbaf7