push: introduce REJECT_FETCH_FIRST and REJECT_NEEDS_FORCE

When we push to update an existing ref, if:

 * the object at the tip of the remote is not a commit; or
 * the object we are pushing is not a commit,

it won't be correct to suggest to fetch, integrate and push again,
as the old and new objects will not "merge".  We should explain that
the push must be forced when there is a non-committish object is
involved in such a case.

If we do not have the current object at the tip of the remote, we do
not even know that object, when fetched, is something that can be
merged.  In such a case, suggesting to pull first just like
non-fast-forward case may not be technically correct, but in
practice, most such failures are seen when you try to push your work
to a branch without knowing that somebody else already pushed to
update the same branch since you forked, so "pull first" would work
as a suggestion most of the time.  And if the object at the tip is
not a commit, "pull first" will fail, without making any permanent
damage.  As a side effect, it also makes the error message the user
will get during the next "push" attempt easier to understand, now
the user is aware that a non-commit object is involved.

In these cases, the current code already rejects such a push on the
client end, but we used the same error and advice messages as the
ones used when rejecting a non-fast-forward push, i.e. pull from
there and integrate before pushing again.

Introduce new rejection reasons and reword the messages
appropriately.

[jc: with help by Peff on message details]

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/transport.c b/transport.c
index 585ebcd2bf..5105562d6e 100644
--- a/transport.c
+++ b/transport.c
@@ -699,6 +699,14 @@ static int print_one_push_status(struct ref *ref, const char *dest, int count, i
 		print_ref_status('!', "[rejected]", ref, ref->peer_ref,
 						 "already exists", porcelain);
 		break;
+	case REF_STATUS_REJECT_FETCH_FIRST:
+		print_ref_status('!', "[rejected]", ref, ref->peer_ref,
+						 "fetch first", porcelain);
+		break;
+	case REF_STATUS_REJECT_NEEDS_FORCE:
+		print_ref_status('!', "[rejected]", ref, ref->peer_ref,
+						 "needs force", porcelain);
+		break;
 	case REF_STATUS_REMOTE_REJECT:
 		print_ref_status('!', "[remote rejected]", ref,
 						 ref->deletion ? NULL : ref->peer_ref,
@@ -750,6 +758,10 @@ void transport_print_push_status(const char *dest, struct ref *refs,
 				*reject_reasons |= REJECT_NON_FF_OTHER;
 		} else if (ref->status == REF_STATUS_REJECT_ALREADY_EXISTS) {
 			*reject_reasons |= REJECT_ALREADY_EXISTS;
+		} else if (ref->status == REF_STATUS_REJECT_FETCH_FIRST) {
+			*reject_reasons |= REJECT_FETCH_FIRST;
+		} else if (ref->status == REF_STATUS_REJECT_NEEDS_FORCE) {
+			*reject_reasons |= REJECT_NEEDS_FORCE;
 		}
 	}
 }