git-cherry-pick: Add keep-redundant-commits option

The git-cherry-pick --allow-empty command by default only preserves empty
commits that were originally empty, i.e only those commits for which
<commit>^{tree} and <commit>^^{tree} are equal.  By default commits which are
non-empty, but were made empty by the inclusion of a prior commit on the current
history are filtered out.  This option allows us to override that behavior and
include redundant commits as empty commits in the change history.

Note that this patch changes the default behavior of git cherry-pick slightly.
Prior to this patch all commits in a cherry-pick sequence were applied and git
commit was run.  The implication here was that, if a commit was redundant, and
the commit did not trigger the fast forward logic, the git commit operation, and
therefore the git cherry-pick operation would fail, displaying the cherry pick
advice (i.e. run git commit --allow-empty).  With this patch however, such
redundant commits are automatically skipped without stopping, unless
--keep-redundant-commits is specified, in which case, they are automatically
applied as empty commits.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/builtin/revert.c b/builtin/revert.c
index 06b00e6f8..b0b9b1a4e 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -115,13 +115,15 @@ static void parse_args(int argc, const char **argv, struct replay_opts *opts)
 		OPT_END(),
 		OPT_END(),
 		OPT_END(),
+		OPT_END(),
 	};
 
 	if (opts->action == REPLAY_PICK) {
 		struct option cp_extra[] = {
 			OPT_BOOLEAN('x', NULL, &opts->record_origin, "append commit name"),
 			OPT_BOOLEAN(0, "ff", &opts->allow_ff, "allow fast-forward"),
-			OPT_BOOLEAN(0, "allow-empty", &opts->allow_empty, "preserve empty commits"),
+			OPT_BOOLEAN(0, "allow-empty", &opts->allow_empty, "preserve initially empty commits"),
+			OPT_BOOLEAN(0, "keep-redundant-commits", &opts->keep_redundant_commits, "keep redundant, empty commits"),
 			OPT_END(),
 		};
 		if (parse_options_concat(options, ARRAY_SIZE(options), cp_extra))
@@ -139,6 +141,10 @@ static void parse_args(int argc, const char **argv, struct replay_opts *opts)
 				"--abort", rollback,
 				NULL);
 
+	/* implies allow_empty */
+	if (opts->keep_redundant_commits)
+		opts->allow_empty = 1;
+
 	/* Set the subcommand */
 	if (remove_state)
 		opts->subcommand = REPLAY_REMOVE_STATE;