A few more options for git-cat-file

This adds '-e' option to git-cat-file, to test for the existence
of the object.

This also cleans up the option-parsing in git-cat-file slightly.

[jc: HPA version had -n option which did rev-parse --verify; the
real value of this patch is the option parsing cleanup.]

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-cat-file.txt

@@ -8,7 +8,7 @@ git-cat-file - Provide content or type information for repository objects
 
 SYNOPSIS
 --------
-'git-cat-file' (-t | -s | <type>) <object>
+'git-cat-file' (-t | -s | -e | <type>) <object>
 
 DESCRIPTION
 -----------
@@ -29,6 +29,10 @@ OPTIONS
 	Instead of the content, show the object size identified by
 	<object>.
 
+-e::
+	Suppress all output; instead exit with zero status if <object>
+	exists and is a valid object.
+
 <type>::
 	Typically this matches the real type of <object> but asking
 	for a type that can trivially be dereferenced from the given
@@ -39,8 +43,11 @@ OPTIONS
 
 OUTPUT
 ------
-If '-t' is specified, one of the <type>.  If '-s' is specified,
-the size of the <object> in bytes.
+If '-t' is specified, one of the <type>.
+
+If '-s' is specified, the size of the <object> in bytes.
+
+If '-e' is specified, no output.
 
 Otherwise the raw (though uncompressed) contents of the <object> will
 be returned.

cat-file.c

@@ -11,27 +11,44 @@ int main(int argc, char **argv)
 	char type[20];
 	void *buf;
 	unsigned long size;
+	int opt;
 
 	setup_git_directory();
 	if (argc != 3 || get_sha1(argv[2], sha1))
-		usage("git-cat-file [-t | -s | <type>] <sha1>");
-
-	if (!strcmp("-t", argv[1]) || !strcmp("-s", argv[1])) {
-		if (!sha1_object_info(sha1, type,
-				      argv[1][1] == 's' ? &size : NULL)) {
-			switch (argv[1][1]) {
-			case 't':
-				printf("%s\n", type);
-				break;
-			case 's':
-				printf("%lu\n", size);
-				break;
-			}
+		usage("git-cat-file [-t|-s|-e|<type>] <sha1>");
+
+	opt = 0;
+	if ( argv[1][0] == '-' ) {
+		opt = argv[1][1];
+		if ( !opt || argv[1][2] )
+			opt = -1; /* Not a single character option */
+	}
+
+	buf = NULL;
+	switch (opt) {
+	case 't':
+		if (!sha1_object_info(sha1, type, NULL)) {
+			printf("%s\n", type);
 			return 0;
 		}
-		buf = NULL;
-	} else {
+		break;
+
+	case 's':
+		if (!sha1_object_info(sha1, type, &size)) {
+			printf("%lu\n", size);
+			return 0;
+		}
+		break;
+
+	case 'e':
+		return !has_sha1_file(sha1);
+
+	case 0:
 		buf = read_object_with_reference(sha1, argv[1], &size, NULL);
+		break;
+
+	default:
+		die("git-cat-file: unknown option: %s\n", argv[1]);
 	}
 
 	if (!buf)