builtin rebase: support `ignore-date` option

This commit adds support for `--ignore-date` which is passed to `git am`
to easily change the dates of the rebased commits.

Signed-off-by: Pratik Karki <predatoramigo@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/rebase.c

@@ -527,6 +527,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		ACTION_SHOW_CURRENT_PATCH,
 	} action = NO_ACTION;
 	int committer_date_is_author_date = 0;
+	int ignore_date = 0;
 	int ignore_whitespace = 0;
 	struct option builtin_rebase_options[] = {
 		OPT_STRING(0, "onto", &options.onto_name,
@@ -550,6 +551,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		OPT_BOOL(0, "committer-date-is-author-date",
 			 &committer_date_is_author_date,
 			 N_("passed to 'git am'")),
+		OPT_BOOL(0, "ignore-date", &ignore_date,
+			 N_("passed to 'git am'")),
 		OPT_BIT('f', "force-rebase", &options.flags,
 			N_("cherry-pick all commits, even if unchanged"),
 			REBASE_FORCE),
@@ -779,6 +782,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	if (ignore_whitespace)
 		strbuf_addstr(&options.git_am_opt, " --ignore-whitespace");
 
+	if (ignore_date) {
+		strbuf_addstr(&options.git_am_opt, " --ignore-date");
+		options.flags |= REBASE_FORCE;
+	}
+
 	switch (options.type) {
 	case REBASE_MERGE:
 	case REBASE_INTERACTIVE: