From: Phillip Wood <redacted>

As part of the on-going effort to retire the apply rebase backend teach
the merge backend how to handle --committer-date-is-author-date.

Original-patch-by: Rohit Ashiwal [off-list ref]
Signed-off-by: Phillip Wood <redacted>
---
 Documentation/git-rebase.txt           | 10 +++--
 builtin/rebase.c                       | 16 ++++---
 sequencer.c                            | 60 +++++++++++++++++++++++++-
 sequencer.h                            |  1 +
 t/t3422-rebase-incompatible-options.sh |  1 -
 t/t3436-rebase-more-options.sh         | 56 ++++++++++++++++++++++++
 6 files changed, 133 insertions(+), 11 deletions(-)

-%<-

diff --git a/sequencer.c b/sequencer.c
index 6fd2674632..3bb80d7414 100644
--- a/sequencer.c
+++ b/sequencer.c

@@ -149,6 +149,7 @@ static GIT_PATH_FUNC(rebase_path_refs_to_delete, "rebase-merge/refs-to-delete")
  * command-line.
  */
 static GIT_PATH_FUNC(rebase_path_gpg_sign_opt, "rebase-merge/gpg_sign_opt")
+static GIT_PATH_FUNC(rebase_path_cdate_is_adate, "rebase-merge/cdate_is_adate")
 static GIT_PATH_FUNC(rebase_path_orig_head, "rebase-merge/orig-head")
 static GIT_PATH_FUNC(rebase_path_verbose, "rebase-merge/verbose")
 static GIT_PATH_FUNC(rebase_path_quiet, "rebase-merge/quiet")

@@ -872,6 +873,22 @@ static char *get_author(const char *message)
 	return NULL;
 }
 
+static const char *author_date_from_env_array(const struct argv_array *env)
+{
+	int i;
+	const char *date;
+
+	for (i = 0; i < env->argc; i++)
+		if (skip_prefix(env->argv[i],
+				"GIT_AUTHOR_DATE=", &date))
+			return date;
+	/*
+	 * If GIT_AUTHOR_DATE is missing we should have already errored out when
+	 * reading the script
+	 */
+	BUG("GIT_AUTHOR_DATE missing from author script");
+}
+

 static const char staged_changes_advice[] =
 N_("you have staged changes in your working tree\n"
 "If these changes are meant to be squashed into the previous commit, run:\n"

@@ -938,6 +955,10 @@ static int run_git_commit(struct repository *r,
 			     gpg_opt, gpg_opt);
 	}
 
+	if (opts->committer_date_is_author_date)
+		argv_array_pushf(&cmd.env_array, "GIT_COMMITTER_DATE=%s",
+				 author_date_from_env_array(&cmd.env_array));
+
 	argv_array_push(&cmd.args, "commit");
 
 	if (!(flags & VERIFY_MSG))

@@ -1321,7 +1342,6 @@ static int try_to_commit(struct repository *r,
 
 	if (parse_head(r, &current_head))
 		return -1;
-