diff: trivial fix for --output file error message

The option argument is either after the equal sign in --output=... or in
the next command-line argument. optarg is the reliable way to access it.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/diff.c b/diff.c
index 9a5c77c13ff3406a85e8a94f309a639529f2d88b..0e2e872e0bb6b82d08e4dc6415afe875ccccc367 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -3310,7 +3310,7 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
        else if ((argcount = parse_long_opt("output", av, &optarg))) {
                options->file = fopen(optarg, "w");
                if (!options->file)
-                       die_errno("Could not open '%s'", arg + strlen("--output="));
+                       die_errno("Could not open '%s'", optarg);
                options->close_file = 1;
                return argcount;
        } else