[PATCH] A few more options for git-cat-file

[PATCH] A few more options for git-cat-file

[H. Peter Anvin]

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This adds the following options to git-cat-file:

-n, to get the canonical name of a resource.  This is for one thing 
useful in tagging scripts.

-e, to test for the existence of a file.

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

Signed-off-by: H. Peter Anvin <hpa@zytor.com>


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diff --git a/Documentation/git-cat-file.txt b/Documentation/git-cat-file.txt
index ab4dcae..a59e513 100644
--- a/Documentation/git-cat-file.txt
+++ b/Documentation/git-cat-file.txt
@@ -8,7 +8,7 @@ git-cat-file - Provide content or type i
 
 SYNOPSIS
 --------
-'git-cat-file' (-t | -s | <type>) <object>
+'git-cat-file' (-t | -s | -n | -e | <type>) <object>
 
 DESCRIPTION
 -----------
@@ -29,6 +29,13 @@ OPTIONS
 	Instead of the content, show the object size identified by
 	<object>.
 
+-n::
+	Instead of the content, show the canoncical name of <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 +46,14 @@ 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 '-n' is specified, the canoncial name (40-character SHA1
+hexadecimal string) of the object.
+
+If '-e' is specified, no output.
 
 Otherwise the raw (though uncompressed) contents of the <object> will
 be returned.
diff --git a/cat-file.c b/cat-file.c
index d775a15..23fbd28 100644
--- a/cat-file.c
+++ b/cat-file.c
@@ -11,27 +11,48 @@ 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>");
+		usage("git-cat-file [-t|-s|-n|-e|<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;
-			}
+	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 'n':
+		printf("%s\n", sha1_to_hex(sha1));
+		return 0;
+
+	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)

Re: [PATCH] A few more options for git-cat-file

[Junio C Hamano]

"H. Peter Anvin" <hpa@zytor.com> writes:

> This adds the following options to git-cat-file:
>
> -n, to get the canonical name of a resource.  This is for one thing 
> useful in tagging scripts.

Isn't "git-rev-parse --verify" good enough?

> -e, to test for the existence of a file.

This might be useful and cleaner than "cat-file -s >/dev/null"
but marginally so.  While reading the whole file and discarding
that to /dev/null is wasteful and would go against tastes of
many people, -t and -s flags do not need to read the whole thing
and not so expensive.

Re: [PATCH] A few more options for git-cat-file

[H. Peter Anvin]

Junio C Hamano wrote:
> "H. Peter Anvin" <hpa@zytor.com> writes:
> 
> 
>>This adds the following options to git-cat-file:
>>
>>-n, to get the canonical name of a resource.  This is for one thing 
>>useful in tagging scripts.
> 
> Isn't "git-rev-parse --verify" good enough?
> 

Ah, yes.  Except for the fact that I couldn't find it when I looked for 
a command that did that.  git-rev-parse seems like an eclectic mixture 
of stuff, and the name isn't very clear as to what it does.

> 
>>-e, to test for the existence of a file.
> 
> This might be useful and cleaner than "cat-file -s >/dev/null"
> but marginally so.  While reading the whole file and discarding
> that to /dev/null is wasteful and would go against tastes of
> many people, -t and -s flags do not need to read the whole thing
> and not so expensive.

Still, -e as implemented here is definitely cheaper.

	-hpa