[RFC PATCH 2/2] set-head: do not update if there is no change

[Bence Ferdinandy <bence@ferdinandy.com>]

Currently, even if there is no actual change to remote/HEAD calling
remote set-head will overwrite the appropriate file and if set to --auto
will also print a message saying "remote/HEAD set to branch", which
implies something was changed. In contrast, on a nil operation e.g. pull
will clearly state that nothing was done, while fetch will not output
anything.

Change the behaviour of remote set-head so that the reference is only
updated if it actually needs to change. Since set-head --auto is
essentially a fetch-like operation, align it's behaviour with fetch and
only print output if something was actually done.

Signed-off-by: Bence Ferdinandy <bence@ferdinandy.com>
---
 builtin/remote.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/builtin/remote.c b/builtin/remote.c
index 35c54dd103..e220e51b84 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -1400,8 +1400,8 @@ static int show(int argc, const char **argv, const char *prefix)
 
 static int set_head(int argc, const char **argv, const char *prefix)
 {
-	int i, opt_a = 0, opt_d = 0, result = 0;
-	struct strbuf buf = STRBUF_INIT, buf2 = STRBUF_INIT;
+	int i, opt_a = 0, opt_d = 0, is_ref_changed = 0, result = 0;
+	struct strbuf buf = STRBUF_INIT, buf2 = STRBUF_INIT, buf3 = STRBUF_INIT;
 	char *head_name = NULL;
 
 	struct option options[] = {
@@ -1440,12 +1440,14 @@ static int set_head(int argc, const char **argv, const char *prefix)
 
 	if (head_name) {
 		strbuf_addf(&buf2, "refs/remotes/%s/%s", argv[0], head_name);
+		refs_read_symbolic_ref(get_main_ref_store(the_repository),buf.buf,&buf3);
+		is_ref_changed = strcmp(buf2.buf,buf3.buf);
 		/* make sure it's valid */
 		if (!refs_ref_exists(get_main_ref_store(the_repository), buf2.buf))
 			result |= error(_("Not a valid ref: %s"), buf2.buf);
-		else if (refs_update_symref(get_main_ref_store(the_repository), buf.buf, buf2.buf, "remote set-head"))
+		else if (is_ref_changed && refs_update_symref(get_main_ref_store(the_repository), buf.buf, buf2.buf, "remote set-head"))
 			result |= error(_("Could not setup %s"), buf.buf);
-		else if (opt_a)
+		else if (opt_a && is_ref_changed)
 			printf("%s/HEAD set to %s\n", argv[0], head_name);
 		free(head_name);
 	}
-- 
2.46.0