[PATCH 4/9] git-cat-file: Add --stdin option

@@ -8,7 +8,7 @@ git-cat-file - Provide content or type/size information for repository objects
 
 SYNOPSIS
 --------
-'git-cat-file' [-t | -s | -e | -p | <type>] <object>
+'git-cat-file' [-t | -s | -e | -p | <type>] [--stdin | <object>]
 
 DESCRIPTION
 -----------

@@ -23,6 +23,10 @@ OPTIONS
 	For a more complete list of ways to spell object names, see
 	"SPECIFYING REVISIONS" section in gitlink:git-rev-parse[1].
 
+--stdin::
+	Read object names from stdin instead of specifying one on the
+	command line.
+
 -t::
 	Instead of the content, show the object type identified by
 	<object>.

@@ -143,12 +143,14 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name)
 	return 0;
 }
 
-static const char cat_file_usage[] = "git-cat-file [-t|-s|-e|-p|<type>] <sha1>";
+static const char cat_file_usage[] = "git-cat-file [-t|-s|-e|-p|<type>] [--stdin | <sha1>]";
 
 int cmd_cat_file(int argc, const char **argv, const char *prefix)
 {
 	int i, opt = 0;
+	int read_stdin = 0;
 	const char *exp_type = 0, *obj_name = 0;
+	struct strbuf buf;
 
 	git_config(git_default_config);
 

@@ -161,6 +163,11 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
 			continue;
 		}
 
+		if (!strcmp(arg, "--stdin")) {
+		    read_stdin = 1;
+		    continue;
+		}
+
 		if (arg[0] == '-')
 			usage(cat_file_usage);
 

@@ -169,15 +176,26 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
 			continue;
 		}
 
-		if (obj_name)
+		if (obj_name || read_stdin)
 			usage(cat_file_usage);
 
 		obj_name = arg;
 		break;
 	}
 
-	if (!exp_type || !obj_name)
+	if (!read_stdin) {
+	    if (!exp_type || !obj_name)
 		usage(cat_file_usage);
+	    return cat_one_file(opt, exp_type, obj_name);
+	}
 
-	return cat_one_file(opt, exp_type, obj_name);
+	strbuf_init(&buf, 0);
+	while (strbuf_getline(&buf, stdin, '\n') != EOF) {
+		int error = cat_one_file(opt, exp_type, buf.buf);
+		if (error)
+			return error;
+	}
+	strbuf_release(&buf);
+
+	return 0;
 }

@@ -88,4 +88,18 @@ test_expect_success \
     "Reach a blob from a tag pointing to it" \
     "test \"$hello_content\" = \"$(git cat-file blob $tag_sha1)\""
 
+sha1s="$hello_sha1
+$tree_sha1
+$commit_sha1
+$tag_sha1"
+
+sizes="$hello_size
+$tree_size
+$commit_size
+$tag_size"
+
+test_expect_success \
+    "Pass object hashes on stdin" \
+    "test \"$sizes\" = \"$(echo "$sha1s" | git cat-file -s --stdin)\""
+
 test_done