diff: convert --check to use a hunk callback

The "diff --check" code needs to know the line number on which each hunk
starts in order to generate its output. We get that now by parsing the
hunk header line generated by xdiff, but it's much simpler to just pass
it directly using a hunk callback.

Signed-off-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: peff

diff.c

@@ -3101,6 +3101,15 @@ static int is_conflict_marker(const char *line, int marker_size, unsigned long l
 	return 1;
 }
 
+static void checkdiff_consume_hunk(void *priv,
+				   long ob, long on, long nb, long nn,
+				   const char *func, long funclen)
+
+{
+	struct checkdiff_t *data = priv;
+	data->lineno = nb - 1;
+}
+
 static void checkdiff_consume(void *priv, char *line, unsigned long len)
 {
 	struct checkdiff_t *data = priv;
@@ -3136,12 +3145,6 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
 			      data->o->file, set, reset, ws);
 	} else if (line[0] == ' ') {
 		data->lineno++;
-	} else if (line[0] == '@') {
-		char *plus = strchr(line, '+');
-		if (plus)
-			data->lineno = strtol(plus, NULL, 10) - 1;
-		else
-			die("invalid diff");
 	}
 }
 
@@ -3650,8 +3653,9 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
 		memset(&xecfg, 0, sizeof(xecfg));
 		xecfg.ctxlen = 1; /* at least one context line */
 		xpp.flags = 0;
-		if (xdi_diff_outf(&mf1, &mf2, NULL, checkdiff_consume,
-				  &data, &xpp, &xecfg))
+		if (xdi_diff_outf(&mf1, &mf2, checkdiff_consume_hunk,
+				  checkdiff_consume, &data,
+				  &xpp, &xecfg))
 			die("unable to generate checkdiff for %s", one->path);
 
 		if (data.ws_rule & WS_BLANK_AT_EOF) {