built-in tar-tree and remote tar-tree

This makes tar-tree a built-in.  As an added bonus, you can now
say:

	git tar-tree --remote=remote-repository <ent> [<base>]

This does not work with git-daemon yet, but should work with
localhost and git over ssh transports.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-upload-tar.c

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2006 Junio C Hamano
+ */
+#include "cache.h"
+#include "pkt-line.h"
+#include "exec_cmd.h"
+#include "builtin.h"
+
+static const char upload_tar_usage[] = "git-upload-tar <repo>";
+
+static int nak(const char *reason)
+{
+	packet_write(1, "NACK %s\n", reason);
+	packet_flush(1);
+	return 1;
+}
+
+int cmd_upload_tar(int argc, const char **argv, char **envp)
+{
+	int len;
+	const char *dir = argv[1];
+	char buf[8192];
+	unsigned char sha1[20];
+	char *base = NULL;
+	char hex[41];
+	int ac;
+	const char *av[4];
+
+	if (argc != 2)
+		usage(upload_tar_usage);
+	if (strlen(dir) < sizeof(buf)-1)
+		strcpy(buf, dir); /* enter-repo smudges its argument */
+	else
+		packet_write(1, "NACK insanely long repository name %s\n", dir);
+	if (!enter_repo(buf, 0)) {
+		packet_write(1, "NACK not a git archive %s\n", dir);
+		packet_flush(1);
+		return 1;
+	}
+
+	len = packet_read_line(0, buf, sizeof(buf));
+	if (len < 5 || strncmp("want ", buf, 5))
+		return nak("expected want");
+	if (buf[len-1] == '\n')
+		buf[--len] = 0;
+	if (get_sha1(buf + 5, sha1))
+		return nak("expected sha1");
+        strcpy(hex, sha1_to_hex(sha1));
+
+	len = packet_read_line(0, buf, sizeof(buf));
+	if (len) {
+		if (len < 5 || strncmp("base ", buf, 5))
+			return nak("expected (optional) base");
+		if (buf[len-1] == '\n')
+			buf[--len] = 0;
+		base = strdup(buf + 5);
+		len = packet_read_line(0, buf, sizeof(buf));
+	}
+	if (len)
+		return nak("expected flush");
+
+	packet_write(1, "ACK\n");
+	packet_flush(1);
+
+	ac = 0;
+	av[ac++] = "tar-tree";
+	av[ac++] = hex;
+	if (base)
+		av[ac++] = base;
+	av[ac++] = NULL;
+	execv_git_cmd(av);
+	/* should it return that is an error */
+	return 1;
+}