1 files changed, 58 insertions, 3 deletions

diff --git a/diff.c b/diff.c
index 00b1044d3..e16e0bfc0 100644
--- a/diff.c
+++ b/diff.c
@@ -232,11 +232,16 @@ static char *pprint_rename(const char *a, const char *b)
 	 * name-a => name-b
 	 */
 	if (pfx_length + sfx_length) {
+		int a_midlen = len_a - pfx_length - sfx_length;
+		int b_midlen = len_b - pfx_length - sfx_length;
+		if (a_midlen < 0) a_midlen = 0;
+		if (b_midlen < 0) b_midlen = 0;
+
 		name = xmalloc(len_a + len_b - pfx_length - sfx_length + 7);
 		sprintf(name, "%.*s{%.*s => %.*s}%s",
 			pfx_length, a,
-			len_a - pfx_length - sfx_length, a + pfx_length,
-			len_b - pfx_length - sfx_length, b + pfx_length,
+			a_midlen, a + pfx_length,
+			b_midlen, b + pfx_length,
 			a + len_a - sfx_length);
 	}
 	else {
@@ -558,7 +563,7 @@ static void builtin_diff(const char *name_a,
 
 		ecbdata.label_path = lbl;
 		xpp.flags = XDF_NEED_MINIMAL;
-		xecfg.ctxlen = 3;
+		xecfg.ctxlen = o->context;
 		xecfg.flags = XDL_EMIT_FUNCNAMES;
 		if (!diffopts)
 			;
@@ -1182,6 +1187,7 @@ void diff_setup(struct diff_options *options)
 	options->line_termination = '\n';
 	options->break_opt = -1;
 	options->rename_limit = -1;
+	options->context = 3;
 
 	options->change = diff_change;
 	options->add_remove = diff_addremove;
@@ -1222,11 +1228,60 @@ int diff_setup_done(struct diff_options *options)
 	return 0;
 }
 
+int opt_arg(const char *arg, int arg_short, const char *arg_long, int *val)
+{
+	char c, *eq;
+	int len;
+
+	if (*arg != '-')
+		return 0;
+	c = *++arg;
+	if (!c)
+		return 0;
+	if (c == arg_short) {
+		c = *++arg;
+		if (!c)
+			return 1;
+		if (val && isdigit(c)) {
+			char *end;
+			int n = strtoul(arg, &end, 10);
+			if (*end)
+				return 0;
+			*val = n;
+			return 1;
+		}
+		return 0;
+	}
+	if (c != '-')
+		return 0;
+	arg++;
+	eq = strchr(arg, '=');
+	if (eq)
+		len = eq - arg;
+	else
+		len = strlen(arg);
+	if (!len || strncmp(arg, arg_long, len))
+		return 0;
+	if (eq) {
+		int n;
+		char *end;
+		if (!isdigit(*++eq))
+			return 0;
+		n = strtoul(eq, &end, 10);
+		if (*end)
+			return 0;
+		*val = n;
+	}
+	return 1;
+}
+
 int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 {
 	const char *arg = av[0];
 	if (!strcmp(arg, "-p") || !strcmp(arg, "-u"))
 		options->output_format = DIFF_FORMAT_PATCH;
+	else if (opt_arg(arg, 'U', "unified", &options->context))
+		options->output_format = DIFF_FORMAT_PATCH;
 	else if (!strcmp(arg, "--patch-with-raw")) {
 		options->output_format = DIFF_FORMAT_PATCH;
 		options->with_raw = 1;