replay: allow callers to sign commits

Add a signing-key option to replay_revisions_options and pass it to
commit_tree_extended() when creating replayed commits.

This provides the replay infrastructure for history commands to sign
replayed descendants.

Signed-off-by: Souma <git@5ouma.me>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

replay.c

@@ -85,13 +85,13 @@ static struct commit *create_commit(struct repository *repo,
 				    struct tree *tree,
 				    struct commit *based_on,
 				    struct commit *parent,
-				    enum replay_mode mode)
+				    enum replay_mode mode,
+				    const char *sign_commit)
 {
 	struct object_id ret;
 	struct object *obj = NULL;
 	struct commit_list *parents = NULL;
 	char *author = NULL;
-	char *sign_commit = NULL; /* FIXME: cli users might want to sign again */
 	struct commit_extra_header *extra = NULL;
 	struct strbuf msg = STRBUF_INIT;
 	const char *out_enc = get_commit_output_encoding();
@@ -288,7 +288,8 @@ static struct commit *pick_regular_commit(struct repository *repo,
 					  struct merge_options *merge_opt,
 					  struct merge_result *result,
 					  enum replay_mode mode,
-					  enum replay_empty_commit_action empty)
+					  enum replay_empty_commit_action empty,
+					  const char *sign_commit)
 {
 	struct tree *pickme_tree, *base_tree, *replayed_base_tree;
 
@@ -361,7 +362,8 @@ static struct commit *pick_regular_commit(struct repository *repo,
 		}
 	}
 
-	return create_commit(repo, result->tree, pickme, replayed_base, mode);
+	return create_commit(repo, result->tree, pickme, replayed_base, mode,
+					    sign_commit);
 }
 
 void replay_result_release(struct replay_result *result)
@@ -481,7 +483,8 @@ int replay_revisions(struct rev_info *revs,
 
 			last_commit = pick_regular_commit(revs->repo, commit, base,
 							  &merge_opt, &result,
-							  mode, opts->empty);
+							  mode, opts->empty,
+							  opts->sign_commit);
 		}
 
 		if (!last_commit)

replay.h

@@ -57,6 +57,12 @@ struct replay_revisions_options {
 	 */
 	int contained;
 
+	/*
+	 * Key used to sign newly-created commits. An empty string requests the
+	 * default configured signing key, and NULL disables signing.
+	 */
+	const char *sign_commit;
+
 	/*
 	 * Controls what to do when a replayed commit becomes empty.
 	 * Defaults to REPLAY_EMPTY_COMMIT_DROP.