push: cleanup push rules comment

Rewrite to remove inter-dependencies amongst the rules.

Signed-off-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

remote.c

@@ -1319,27 +1319,29 @@ void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
 			continue;
 		}
 
-		/* This part determines what can overwrite what.
-		 * The rules are:
+		/*
+		 * The below logic determines whether an individual
+		 * refspec A:B can be pushed.  The push will succeed
+		 * if any of the following are true:
 		 *
-		 * (0) you can always use --force or +A:B notation to
-		 *     selectively force individual ref pairs.
+		 * (1) the remote reference B does not exist
 		 *
-		 * (1) if the old thing does not exist, it is OK.
+		 * (2) the remote reference B is being removed (i.e.,
+		 *     pushing :B where no source is specified)
 		 *
-		 * (2) if the destination is under refs/tags/ you are
-		 *     not allowed to overwrite it; tags are expected
-		 *     to be static once created
+		 * (3) the update meets all fast-forwarding criteria:
 		 *
-		 * (3) if you do not have the old thing, you are not allowed
-		 *     to overwrite it; you would not know what you are losing
-		 *     otherwise.
+		 *     (a) the destination is not under refs/tags/
+		 *     (b) the old is a commit
+		 *     (c) the new is a descendant of the old
 		 *
-		 * (4) if old is a commit and new is a descendant of old
-		 *     (implying new is commit-ish), it is OK.
+		 *     NOTE: We must actually have the old object in
+		 *     order to overwrite it in the remote reference,
+		 *     and the new object must be commit-ish.  These are
+		 *     implied by (b) and (c) respectively.
 		 *
-		 * (5) regardless of all of the above, removing :B is
-		 *     always allowed.
+		 * (4) it is forced using the +A:B notation, or by
+		 *     passing the --force argument
 		 */
 
 		ref->not_forwardable = !is_forwardable(ref);