branch: reset instead of release a strbuf

Our documentation advises to not re-use a strbuf, after strbuf_release
has been called on it. Use the proper reset instead.

Currently 'strbuf_release' releases and re-initializes the strbuf, so it
is safe, but slow. 'strbuf_reset' only resets the internal length variable,
such that this could also be accounted for as a micro-optimization.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: stefanbeller

builtin/branch.c

@@ -216,7 +216,7 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 		if (!head_rev)
 			die(_("Couldn't look up commit object for HEAD"));
 	}
-	for (i = 0; i < argc; i++, strbuf_release(&bname)) {
+	for (i = 0; i < argc; i++, strbuf_reset(&bname)) {
 		char *target = NULL;
 		int flags = 0;
 
@@ -281,8 +281,9 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 	}
 
 	free(name);
+	strbuf_release(&bname);
 
-	return(ret);
+	return ret;
 }
 
 static int calc_maxwidth(struct ref_array *refs, int remote_bonus)