commit: give advice on empty amend

diff --git a/builtin/commit.c b/builtin/commit.c
index 8dd104ee0b247f5536d02d54a932acfcbaec603b..216ecc91d18457aad91156bde46dfe669dbb828b 100644 (file)
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -48,6 +48,11 @@ static const char implicit_ident_advice[] =
 "\n"
 "    git commit --amend --author='Your Name <you@example.com>'\n";
 
+static const char empty_amend_advice[] =
+"You asked to amend the most recent commit, but doing so would make\n"
+"it empty. You can repeat your command with --allow-empty, or you can\n"
+"remove the commit entirely with \"git reset HEAD^\".\n";
+
 static unsigned char head_sha1[20];
 
 static char *use_message_buffer;
@@ -307,7 +312,7 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, int
         * (B) on failure, rollback the real index.
         */
        if (all || (also && pathspec && *pathspec)) {
-               int fd = hold_locked_index(&index_lock, 1);
+               fd = hold_locked_index(&index_lock, 1);
                add_files_to_cache(also ? prefix : NULL, pathspec, 0);
                refresh_cache_or_die(refresh_flags);
                if (write_cache(fd, active_cache, active_nr) ||
@@ -322,8 +327,8 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, int
         *
         * (1) return the name of the real index file.
         *
-        * The caller should run hooks on the real index, and run
-        * hooks on the real index, and create commit from the_index.
+        * The caller should run hooks on the real index,
+        * and create commit from the_index.
         * We still need to refresh the index here.
         */
        if (!pathspec || !*pathspec) {
@@ -693,6 +698,8 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
        if (!commitable && !in_merge && !allow_empty &&
            !(amend && is_a_merge(head_sha1))) {
                run_status(stdout, index_file, prefix, 0, s);
+               if (amend)
+                       fputs(empty_amend_advice, stderr);
                return 0;
        }