merge: do not launch an editor on "--no-edit $tag"

When the user explicitly asked us not to, don't launch an editor.

But do everything else the same way as the "edit" case, i.e. leave the
comment with verification result in the log template and record the
mergesig in the resulting merge commit for later inspection.

Based on initiail analysis by Jonathan Nieder.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/merge.c

@@ -48,7 +48,7 @@ static const char * const builtin_merge_usage[] = {
 
 static int show_diffstat = 1, shortlog_len = -1, squash;
 static int option_commit = 1, allow_fast_forward = 1;
-static int fast_forward_only, option_edit;
+static int fast_forward_only, option_edit = -1;
 static int allow_trivial = 1, have_message;
 static int overwrite_ignore = 1;
 static struct strbuf merge_msg = STRBUF_INIT;
@@ -193,7 +193,7 @@ static struct option builtin_merge_options[] = {
 		"create a single commit instead of doing a merge"),
 	OPT_BOOLEAN(0, "commit", &option_commit,
 		"perform a commit if the merge succeeds (default)"),
-	OPT_BOOLEAN('e', "edit", &option_edit,
+	OPT_BOOL('e', "edit", &option_edit,
 		"edit message before committing"),
 	OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 		"allow fast-forward (default)"),
@@ -1287,11 +1287,15 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		    merge_remote_util(commit) &&
 		    merge_remote_util(commit)->obj &&
 		    merge_remote_util(commit)->obj->type == OBJ_TAG) {
-			option_edit = 1;
+			if (option_edit < 0)
+				option_edit = 1;
 			allow_fast_forward = 0;
 		}
 	}
 
+	if (option_edit < 0)
+		option_edit = 0;
+
 	if (!use_strategies) {
 		if (!remoteheads->next)
 			add_strategies(pull_twohead, DEFAULT_TWOHEAD);

t/t7600-merge.sh

@@ -683,4 +683,16 @@ test_expect_success GPG 'merge --ff-only tag' '
 	test_cmp actual expect
 '
 
+test_expect_success GPG 'merge --no-edit tag should skip editor' '
+	git reset --hard c0 &&
+	git commit --allow-empty -m "A newer commit" &&
+	git tag -f -s -m "A newer commit" signed &&
+	git reset --hard c0 &&
+
+	EDITOR=false git merge --no-edit signed &&
+	git rev-parse signed^0 >expect &&
+	git rev-parse HEAD^2 >actual &&
+	test_cmp actual expect
+'
+
 test_done