Merge branch 'jk/rev-list-empty-input' into maint

"git log --tag=no-such-tag" showed log starting from HEAD, which
has been fixed---it now shows nothing.

* jk/rev-list-empty-input:
  revision: do not fallback to default when rev_input_given is set
  rev-list: don't show usage when we see empty ref patterns
  revision: add rev_input_given flag
  t6018: flesh out empty input/output rev-list tests

builtin/rev-list.c

@@ -352,7 +352,8 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 
 	if ((!revs.commits && reflog_walk_empty(revs.reflog_info) &&
 	     (!(revs.tag_objects || revs.tree_objects || revs.blob_objects) &&
-	      !revs.pending.nr)) ||
+	      !revs.pending.nr) &&
+	     !revs.rev_input_given) ||
 	    revs.diff)
 		usage(rev_list_usage);
 

revision.c

@@ -1166,6 +1166,7 @@ static void init_all_refs_cb(struct all_refs_cb *cb, struct rev_info *revs,
 {
 	cb->all_revs = revs;
 	cb->all_flags = flags;
+	revs->rev_input_given = 1;
 }
 
 void clear_ref_exclusion(struct string_list **ref_excludes_p)
@@ -2313,7 +2314,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 		opt->tweak(revs, opt);
 	if (revs->show_merge)
 		prepare_show_merge(revs);
-	if (revs->def && !revs->pending.nr && !got_rev_arg) {
+	if (revs->def && !revs->pending.nr && !revs->rev_input_given && !got_rev_arg) {
 		struct object_id oid;
 		struct object *object;
 		struct object_context oc;

revision.h

@@ -71,6 +71,13 @@ struct rev_info {
 	const char *def;
 	struct pathspec prune_data;
 
+	/*
+	 * Whether the arguments parsed by setup_revisions() included any
+	 * "input" revisions that might still have yielded an empty pending
+	 * list (e.g., patterns like "--all" or "--glob").
+	 */
+	int rev_input_given;
+
 	/* topo-sort */
 	enum rev_sort_order sort_order;
 

t/t4202-log.sh

@@ -1523,6 +1523,12 @@ test_expect_success 'log diagnoses bogus HEAD' '
 	test_i18ngrep broken stderr
 '
 
+test_expect_success 'log does not default to HEAD when rev input is given' '
+	>expect &&
+	git log --branches=does-not-exist >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'set up --source tests' '
 	git checkout --orphan source-a &&
 	test_commit one &&

t/t6018-rev-list-glob.sh

@@ -255,27 +255,19 @@ test_expect_success 'rev-list accumulates multiple --exclude' '
 	compare rev-list "--exclude=refs/remotes/* --exclude=refs/tags/* --all" --branches
 '
 
-
-# "git rev-list<ENTER>" is likely to be a bug in the calling script and may
-# deserve an error message, but do cases where set of refs programmatically
-# given using globbing and/or --stdin need to fail with the same error, or
-# are we better off reporting a success with no output?  The following few
-# tests document the current behaviour to remind us that we might want to
-# think about this issue.
-
-test_expect_failure 'rev-list may want to succeed with empty output on no input (1)' '
+test_expect_failure 'rev-list should succeed with empty output on empty stdin' '
 	>expect &&
 	git rev-list --stdin <expect >actual &&
 	test_cmp expect actual
 '
 
-test_expect_failure 'rev-list may want to succeed with empty output on no input (2)' '
+test_expect_success 'rev-list should succeed with empty output with all refs excluded' '
 	>expect &&
 	git rev-list --exclude=* --all >actual &&
 	test_cmp expect actual
 '
 
-test_expect_failure 'rev-list may want to succeed with empty output on no input (3)' '
+test_expect_success 'rev-list should succeed with empty output with empty --all' '
 	(
 		test_create_repo empty &&
 		cd empty &&
@@ -285,6 +277,12 @@ test_expect_failure 'rev-list may want to succeed with empty output on no input
 	)
 '
 
+test_expect_success 'rev-list should succeed with empty output with empty glob' '
+	>expect &&
+	git rev-list --glob=does-not-match-anything >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'shortlog accepts --glob/--tags/--remotes' '
 
 	compare shortlog "subspace/one subspace/two" --branches=subspace &&