[RFC] git-fsck-cache argument processing

["Sean" <seanlkml@sympatico.ca>]

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Here is a first crack at using argp as suggested by Jeff Garzik to
implement argument processing as requested by Junio and Linus.  Each of
the long arguments have been given a single character equivalent as well.

This patch only converts fsck-cache to use argp in case anyone has
objections to the basic format or style.  The patch includes a version
number inside of fsck-cache.c; this should really be in a separate include
file so you can run any command with --version and get the same answer.

With this change you have:

$ git-fsck-cache -?
Usage: git-fsck-cache [OPTION...] [HEAD-SHA1...]
git-fsck-cache - repository consistency check

 -c, --cache            Mark all objects referenced by cache as reachable
 -d, --delta-depth      Show the maximum length of delta chains
 -r, --root             Show root objects, ie. those without parents
 -t, --tags             Show revision tags
 -u, --unreachable      Show missing objects or deltas
 -?, --help             Give this help list
     --usage            Give a short usage message
 -V, --version          Print program version

And the following should work as expected:

$ git-fsck-cache -crudt


fsck-cache.c |   64
+++++++++++++++++++++++++++++++++++------------------------
1 files changed, 39 insertions(+), 25 deletions(-)

Sean

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fsck-cache.c: needs update
Index: fsck-cache.c
===================================================================
--- 58741c69570705801db4b785681790d636475695/fsck-cache.c  (mode:100644)
+++ uncommitted/fsck-cache.c  (mode:100644)
@@ -1,5 +1,7 @@
 #include <sys/types.h>
 #include <dirent.h>
+#include <argp.h>
+const char *argp_program_version = "git 1.0";
 
 #include "cache.h"
 #include "commit.h"
@@ -407,36 +409,48 @@
 	find_file_objects(git_dir, "refs");
 }
 
+#define O_UNREACH 'u'
+#define O_TAGS 't'
+#define O_ROOT 'r'
+#define O_DELTA 'd'
+#define O_CACHE 'c'
+
+static const char doc[] = "Perform repository consistency check";
+
+static struct argp_option options[] = {
+ {"unreachable", O_UNREACH, 0, 0, "Show missing objects or deltas"},
+ {"tags", O_TAGS, 0, 0, "Show revision tags"},
+ {"root", O_ROOT, 0, 0, "Show root objects, ie. those without parents"},
+ {"delta-depth", O_DELTA, 0, 0, "Show the maximum length of delta chains"},
+ {"cache", O_CACHE, 0, 0, "Mark all objects referenced by cache as reachable"},
+ { }
+};
+
+static error_t parse_opt (int key, char *arg, struct argp_state *state)
+{
+	switch (key) {
+	case O_UNREACH:		show_unreachable = 1; break;
+	case O_TAGS:		show_tags = 1; break;
+	case O_ROOT:		show_root = 1; break;
+	case O_DELTA:		show_max_delta_depth = 1; break;
+	case O_CACHE:		keep_cache_objects = 1; break;
+	case ARGP_KEY_ARG:	state->next = state->argc; break;
+	default:		return ARGP_ERR_UNKNOWN;
+	}
+	return 0;
+}
+
+static const struct argp argp = { options, parse_opt, "[HEAD-SHA1...]", doc };
+
 int main(int argc, char **argv)
 {
 	int i, heads;
 	char *sha1_dir;
 
-	for (i = 1; i < argc; i++) {
-		const char *arg = argv[i];
-
-		if (!strcmp(arg, "--unreachable")) {
-			show_unreachable = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--tags")) {
-			show_tags = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--root")) {
-			show_root = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--delta-depth")) {
-			show_max_delta_depth = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--cache")) {
-			keep_cache_objects = 1;
-			continue;
-		}
-		if (*arg == '-')
-			usage("git-fsck-cache [--tags] [[--unreachable] [--cache] <head-sha1>*]");
+	error_t rc = argp_parse(&argp, argc, argv, 0, NULL, NULL);
+	if (rc) {
+		fprintf(stderr, "argument failed: %s\n", strerror(rc));
+		return 1;
 	}
 
 	sha1_dir = get_object_directory();