push: add advice for rejected tag reference

Advising the user to fetch and merge only makes sense if the rejected
reference is a branch.  If none of the rejections are for branches, just
tell the user the reference already exists.

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

builtin/push.c

@@ -220,6 +220,10 @@ static const char message_advice_checkout_pull_push[] =
 	   "(e.g. 'git pull') before pushing again.\n"
 	   "See the 'Note about fast-forwards' in 'git push --help' for details.");
 
+static const char message_advice_ref_already_exists[] =
+	N_("Updates were rejected because the destination reference already exists\n"
+	   "in the remote and the update is not a fast-forward.");
+
 static void advise_pull_before_push(void)
 {
 	if (!advice_push_non_ff_current || !advice_push_nonfastforward)
@@ -241,6 +245,11 @@ static void advise_checkout_pull_push(void)
 	advise(_(message_advice_checkout_pull_push));
 }
 
+static void advise_ref_already_exists(void)
+{
+	advise(_(message_advice_ref_already_exists));
+}
+
 static int push_with_options(struct transport *transport, int flags)
 {
 	int err;
@@ -272,6 +281,8 @@ static int push_with_options(struct transport *transport, int flags)
 			advise_use_upstream();
 		else
 			advise_checkout_pull_push();
+	} else if (reject_reasons & REJECT_ALREADY_EXISTS) {
+		advise_ref_already_exists();
 	}
 
 	return 1;

cache.h

@@ -1002,6 +1002,7 @@ struct ref {
 	unsigned int force:1,
 		merge:1,
 		nonfastforward:1,
+		not_forwardable:1,
 		deletion:1;
 	enum {
 		REF_STATUS_NONE = 0,

remote.c

@@ -1279,6 +1279,14 @@ int match_push_refs(struct ref *src, struct ref **dst,
 	return 0;
 }
 
+static inline int is_forwardable(struct ref* ref)
+{
+	if (!prefixcmp(ref->name, "refs/tags/"))
+		return 0;
+
+	return 1;
+}
+
 void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
 	int force_update)
 {
@@ -1316,6 +1324,8 @@ void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
 		 *     always allowed.
 		 */
 
+		ref->not_forwardable = !is_forwardable(ref);
+
 		ref->nonfastforward =
 			!ref->deletion &&
 			!is_null_sha1(ref->old_sha1) &&

transport.c

@@ -740,6 +740,8 @@ void transport_print_push_status(const char *dest, struct ref *refs,
 		    ref->status != REF_STATUS_OK)
 			n += print_one_push_status(ref, dest, n, porcelain);
 		if (ref->status == REF_STATUS_REJECT_NONFASTFORWARD) {
+			if (ref->not_forwardable)
+				*reject_reasons |= REJECT_ALREADY_EXISTS;
 			if (!strcmp(head, ref->name))
 				*reject_reasons |= REJECT_NON_FF_HEAD;
 			else

transport.h

@@ -142,6 +142,7 @@ void transport_set_verbosity(struct transport *transport, int verbosity,
 
 #define REJECT_NON_FF_HEAD     0x01
 #define REJECT_NON_FF_OTHER    0x02
+#define REJECT_ALREADY_EXISTS  0x04
 
 int transport_push(struct transport *connection,
 		   int refspec_nr, const char **refspec, int flags,