diff --no-index: also imitate the exit status of diff(1)

diff sets the exit status to 0 when no changes were found, to 1
when changes were found, and 2 means error.

We imitate this to be able to use "git diff" in the test scripts.
(Actually, keeping in line with the rest of git, -1 is returned
on error, which corresponds to an exit status 255).

To find out if the diff is not empty, a member called
"found_changes" was introduced in struct diff_options, which is
set in builtin_diff() and fn_out_consume().

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/diff.c b/diff.c
index 6bd456ed42..5651152a93 100644
--- a/diff.c
+++ b/diff.c
@@ -382,6 +382,7 @@ struct emit_callback {
 	int nparents, color_diff;
 	const char **label_path;
 	struct diff_words_data *diff_words;
+	int *found_changesp;
 };
 
 static void free_diff_words_data(struct emit_callback *ecbdata)
@@ -501,6 +502,8 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 	const char *set = diff_get_color(ecbdata->color_diff, DIFF_METAINFO);
 	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
 
+	*(ecbdata->found_changesp) = 1;
+
 	if (ecbdata->label_path[0]) {
 		const char *name_a_tab, *name_b_tab;
 
@@ -1098,6 +1101,7 @@ static void builtin_diff(const char *name_a,
 		if (complete_rewrite) {
 			emit_rewrite_diff(name_a, name_b, one, two,
 					o->color_diff);
+			o->found_changes = 1;
 			goto free_ab_and_return;
 		}
 	}
@@ -1115,6 +1119,7 @@ static void builtin_diff(const char *name_a,
 		else
 			printf("Binary files %s and %s differ\n",
 			       lbl[0], lbl[1]);
+		o->found_changes = 1;
 	}
 	else {
 		/* Crazy xdl interfaces.. */
@@ -1127,6 +1132,7 @@ static void builtin_diff(const char *name_a,
 		memset(&ecbdata, 0, sizeof(ecbdata));
 		ecbdata.label_path = lbl;
 		ecbdata.color_diff = o->color_diff;
+		ecbdata.found_changesp = &o->found_changes;
 		xpp.flags = XDF_NEED_MINIMAL | o->xdl_opts;
 		xecfg.ctxlen = o->context;
 		xecfg.flags = XDL_EMIT_FUNCNAMES;