Fix git-runstatus for repositories containing a file named HEAD

The wt_status_print_updated() and wt_status_print_untracked() routines
call setup_revisions() with 'HEAD' being the reference to the tip of the
current branch. However, setup_revisions() gets confused if the branch
also contains a file named 'HEAD' resulting in a fatal error.

Instead, don't pass an argv to setup_revisions() at all; simply give it no
arguments, and make 'HEAD' the default revision.

Bug noticed by Rocco Rutte <pdmef@gmx.net>.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

wt-status.c

@@ -156,10 +156,8 @@ void wt_status_print_initial(struct wt_status *s)
 static void wt_status_print_updated(struct wt_status *s)
 {
 	struct rev_info rev;
-	const char *argv[] = { NULL, NULL, NULL };
-	argv[1] = s->reference;
 	init_revisions(&rev, NULL);
-	setup_revisions(2, argv, &rev, NULL);
+	setup_revisions(0, NULL, &rev, s->reference);
 	rev.diffopt.output_format |= DIFF_FORMAT_CALLBACK;
 	rev.diffopt.format_callback = wt_status_print_updated_cb;
 	rev.diffopt.format_callback_data = s;
@@ -170,9 +168,8 @@ static void wt_status_print_updated(struct wt_status *s)
 static void wt_status_print_changed(struct wt_status *s)
 {
 	struct rev_info rev;
-	const char *argv[] = { NULL, NULL };
 	init_revisions(&rev, "");
-	setup_revisions(1, argv, &rev, NULL);
+	setup_revisions(0, NULL, &rev, NULL);
 	rev.diffopt.output_format |= DIFF_FORMAT_CALLBACK;
 	rev.diffopt.format_callback = wt_status_print_changed_cb;
 	rev.diffopt.format_callback_data = s;
@@ -227,10 +224,8 @@ static void wt_status_print_untracked(const struct wt_status *s)
 static void wt_status_print_verbose(struct wt_status *s)
 {
 	struct rev_info rev;
-	const char *argv[] = { NULL, NULL, NULL };
-	argv[1] = s->reference;
 	init_revisions(&rev, NULL);
-	setup_revisions(2, argv, &rev, NULL);
+	setup_revisions(0, NULL, &rev, s->reference);
 	rev.diffopt.output_format |= DIFF_FORMAT_PATCH;
 	rev.diffopt.detect_rename = 1;
 	run_diff_index(&rev, 1);