make "git unpack-file" a built-in

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-unpack-file.c

@@ -0,0 +1,38 @@
+#include "cache.h"
+#include "blob.h"
+#include "exec_cmd.h"
+
+static char *create_temp_file(unsigned char *sha1)
+{
+	static char path[50];
+	void *buf;
+	enum object_type type;
+	unsigned long size;
+	int fd;
+
+	buf = read_sha1_file(sha1, &type, &size);
+	if (!buf || type != OBJ_BLOB)
+		die("unable to read blob object %s", sha1_to_hex(sha1));
+
+	strcpy(path, ".merge_file_XXXXXX");
+	fd = xmkstemp(path);
+	if (write_in_full(fd, buf, size) != size)
+		die_errno("unable to write temp-file");
+	close(fd);
+	return path;
+}
+
+int cmd_unpack_file(int argc, const char **argv, const char *prefix)
+{
+	unsigned char sha1[20];
+
+	if (argc != 2 || !strcmp(argv[1], "-h"))
+		usage("git unpack-file <sha1>");
+	if (get_sha1(argv[1], sha1))
+		die("Not a valid object name %s", argv[1]);
+
+	git_config(git_default_config, NULL);
+
+	puts(create_temp_file(sha1));
+	return 0;
+}