push: add '-d' as shorthand for '--delete'

"git push" takes "--delete" but does not take a short form "-d",
unlike "git branch" which does take both.  Bring consistency
between them.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-push.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 --------
 [verse]
 'git push' [--all | --mirror | --tags] [--follow-tags] [--atomic] [-n | --dry-run] [--receive-pack=<git-receive-pack>]
-	   [--repo=<repository>] [-f | --force] [--delete] [--prune] [-v | --verbose]
+	   [--repo=<repository>] [-f | --force] [-d | --delete] [--prune] [-v | --verbose]
 	   [-u | --set-upstream]
 	   [--[no-]signed|--sign=(true|false|if-asked)]
 	   [--force-with-lease[=<refname>[:<expect>]]]

builtin/push.c

@@ -540,7 +540,7 @@ int cmd_push(int argc, const char **argv, const char *prefix)
 		OPT_BIT( 0 , "all", &flags, N_("push all refs"), TRANSPORT_PUSH_ALL),
 		OPT_BIT( 0 , "mirror", &flags, N_("mirror all refs"),
 			    (TRANSPORT_PUSH_MIRROR|TRANSPORT_PUSH_FORCE)),
-		OPT_BOOL( 0, "delete", &deleterefs, N_("delete refs")),
+		OPT_BOOL('d', "delete", &deleterefs, N_("delete refs")),
 		OPT_BOOL( 0 , "tags", &tags, N_("push tags (can't be used with --all or --mirror)")),
 		OPT_BIT('n' , "dry-run", &flags, N_("dry run"), TRANSPORT_PUSH_DRY_RUN),
 		OPT_BIT( 0,  "porcelain", &flags, N_("machine-readable output"), TRANSPORT_PUSH_PORCELAIN),