push: add reflog check for "--force-if-includes"

Add a check to verify if the remote-tracking ref of the local branch
is reachable from one of its "reflog" entries.

The check iterates through the local ref's reflog to see if there
is an entry for the remote-tracking ref and collecting any commits
that are seen, into a list; the iteration stops if an entry in the
reflog matches the remote ref or if the entry timestamp is older
the latest entry of the remote ref's "reflog". If there wasn't an
entry found for the remote ref, "in_merge_bases_many()" is called
to check if it is reachable from the list of collected commits.

When a local branch that is based on a remote ref, has been rewound
and is to be force pushed on the remote, "--force-if-includes" runs
a check that ensures any updates to the remote-tracking ref that may
have happened (by push from another repository) in-between the time
of the last update to the local branch (via "git-pull", for instance)
and right before the time of push, have been integrated locally
before allowing a forced update.

If the new option is passed without specifying "--force-with-lease",
or specified along with "--force-with-lease=<refname>:<expect>" it
is a "no-op".

Signed-off-by: Srinidhi Kaushik <shrinidhi.kaushik@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/transport-helper.c b/transport-helper.c
index b573b6c..6157de3 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -827,6 +827,10 @@ static int push_update_ref_status(struct strbuf *buf,
 			status = REF_STATUS_REJECT_STALE;
 			FREE_AND_NULL(msg);
 		}
+		else if (!strcmp(msg, "remote ref updated since checkout")) {
+			status = REF_STATUS_REJECT_REMOTE_UPDATED;
+			FREE_AND_NULL(msg);
+		}
 		else if (!strcmp(msg, "forced update")) {
 			forced = 1;
 			FREE_AND_NULL(msg);
@@ -967,6 +971,7 @@ static int push_refs_with_push(struct transport *transport,
 		case REF_STATUS_REJECT_NONFASTFORWARD:
 		case REF_STATUS_REJECT_STALE:
 		case REF_STATUS_REJECT_ALREADY_EXISTS:
+		case REF_STATUS_REJECT_REMOTE_UPDATED:
 			if (atomic) {
 				reject_atomic_push(remote_refs, mirror);
 				string_list_clear(&cas_options, 0);