parse-opt: fake short strings for callers to believe in.

If we begin to parse -abc and that the parser knew about -a and -b, it
will fake a -c switch for the caller to deal with.

Of course in the case of -acb (supposing -c is not taking an argument) the
caller will have to be especially clever to do the same thing. We could
think about exposing an API to do so if it's really needed, but oh well...
Signed-off-by: NPierre Habouzit <madcoder@debian.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

parse-options.c

 #include "git-compat-util.h"
 #include "parse-options.h"
+#include "cache.h"
 
 #define OPT_SHORT 1
 #define OPT_UNSET 2
@@ -257,6 +258,9 @@ int parse_options_step(struct parse_opt_ctx_t *ctx,
 		       const struct option *options,
 		       const char * const usagestr[])
 {
+	/* we must reset ->opt, unknown short option leave it dangling */
+	ctx->opt = NULL;
+
 	for (; ctx->argc; ctx->argc--, ctx->argv++) {
 		const char *arg = ctx->argv[0];
 
@@ -286,6 +290,13 @@ int parse_options_step(struct parse_opt_ctx_t *ctx,
 				case -1:
 					return parse_options_usage(usagestr, options);
 				case -2:
+					/* fake a short option thing to hide the fact that we may have
+					 * started to parse aggregated stuff
+					 *
+					 * This is leaky, too bad.
+					 */
+					ctx->argv[0] = xstrdup(ctx->opt - 1);
+					*(char *)ctx->argv[0] = '-';
 					return PARSE_OPT_UNKNOWN;
 				}
 			}

parse-options.h

@@ -119,6 +119,11 @@ enum {
 	PARSE_OPT_UNKNOWN,
 };
 
+/*
+ * It's okay for the caller to consume argv/argc in the usual way.
+ * Other fields of that structure are private to parse-options and should not
+ * be modified in any way.
+ */
 struct parse_opt_ctx_t {
 	const char **argv;
 	const char **out;