diff: report bogus input to -C/-M/-B

We already detect invalid input to these functions, but we
simply exit with an error code, never saying anything as
simple as "your input was wrong". Let's fix that.

Before:

  $ git diff -CM
  $ echo $?
  128

After:

  $ git diff -CM
  error: invalid argument to -C: M
  $ echo $?
  128

There should be no problems with having diff_opt_parse print
to stderr, as there is already precedent in complaining
about bogus --color and --output arguments.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/diff.c b/diff.c
index 71efa8edd49fe1c80fb37a0468c68ef5ab0d2596..84876431bc64c72a3e632d40eb8a13d270fc9a56 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -3142,18 +3142,18 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
        /* renames options */
        else if (!prefixcmp(arg, "-B")) {
                if ((options->break_opt = diff_scoreopt_parse(arg)) == -1)
-                       return -1;
+                       return error("invalid argument to -B: %s", arg+2);
        }
        else if (!prefixcmp(arg, "-M")) {
                if ((options->rename_score = diff_scoreopt_parse(arg)) == -1)
-                       return -1;
+                       return error("invalid argument to -M: %s", arg+2);
                options->detect_rename = DIFF_DETECT_RENAME;
        }
        else if (!prefixcmp(arg, "-C")) {
                if (options->detect_rename == DIFF_DETECT_COPY)
                        DIFF_OPT_SET(options, FIND_COPIES_HARDER);
                if ((options->rename_score = diff_scoreopt_parse(arg)) == -1)
-                       return -1;
+                       return error("invalid argument to -C: %s", arg+2);
                options->detect_rename = DIFF_DETECT_COPY;
        }
        else if (!strcmp(arg, "--no-renames"))