Add "git-clone-pack" program to help with "git clone"

Makefile

@@ -43,7 +43,7 @@ PROG=   git-update-cache git-diff-files git-init-db git-write-tree \
 	git-get-tar-commit-id git-apply git-stripspace \
 	git-diff-stages git-rev-parse git-patch-id git-pack-objects \
 	git-unpack-objects git-verify-pack git-receive-pack git-send-pack \
-	git-prune-packed git-fetch-pack git-upload-pack
+	git-prune-packed git-fetch-pack git-upload-pack git-clone-pack
 
 all: $(PROG)
 

clone-pack.c

@@ -0,0 +1,208 @@
+#include "cache.h"
+#include "refs.h"
+#include "pkt-line.h"
+#include <sys/wait.h>
+
+static const char clone_pack_usage[] = "git-clone-pack [host:]directory [heads]*";
+static const char *exec = "git-upload-pack";
+
+struct ref {
+	struct ref *next;
+	unsigned char sha1[20];
+	char name[0];
+};
+
+struct ref *get_remote_refs(int fd, int nr_match, char **match)
+{
+	struct ref *ref_list = NULL, **next_ref = &ref_list;
+
+	for (;;) {
+		static char line[1000];
+		unsigned char sha1[20];
+		struct ref *ref;
+		char *refname;
+		int len;
+
+		len = packet_read_line(fd, line, sizeof(line));
+		if (!len)
+			break;
+		if (line[len-1] == '\n')
+			line[--len] = 0;
+		if (len < 42 || get_sha1_hex(line, sha1))
+			die("git-fetch-pack: protocol error - expected ref descriptor, got '%s¤'", line);
+		refname = line+41;
+		len = len-40;
+		if (nr_match && !path_match(refname, nr_match, match))
+			continue;
+		ref = xmalloc(sizeof(struct ref) + len);
+		ref->next = NULL;
+		memcpy(ref->sha1, sha1, 20);
+		memcpy(ref->name, refname, len);
+		*next_ref = ref;
+		next_ref = &ref->next;
+	}
+	return ref_list;
+}
+
+static void clone_handshake(int fd[2], struct ref *ref)
+{
+	unsigned char sha1[20];
+
+	while (ref) {
+		packet_write(fd[1], "want %s\n", sha1_to_hex(ref->sha1));
+		ref = ref->next;
+	}
+	packet_flush(fd[1]);
+
+	/* We don't have nuttin' */
+	packet_write(fd[1], "done\n");
+	if (get_ack(fd[0], sha1))
+		error("Huh! git-clone-pack got positive ack for %s", sha1_to_hex(sha1));
+}
+
+static int is_master(struct ref *ref)
+{
+	return !strcmp(ref->name, "refs/heads/master");
+}
+
+static void write_one_ref(struct ref *ref)
+{
+	char *path = git_path(ref->name);
+	int fd = open(path, O_CREAT | O_EXCL | O_WRONLY, 0666);
+	char *hex;
+
+	if (fd < 0)
+		die("unable to create ref %s", ref->name);
+	hex = sha1_to_hex(ref->sha1);
+	hex[40] = '\n';
+	if (write(fd, hex, 41) != 41)
+		die("unable to write ref %s", ref->name);
+	close(fd);
+}
+
+static void write_refs(struct ref *ref)
+{
+	struct ref *head = NULL, *head_ptr, *master_ref;
+	char *head_path;
+
+	if (!strcmp(ref->name, "HEAD")) {
+		head = ref;
+		ref = ref->next;
+	}
+	head_ptr = NULL;
+	master_ref = NULL;
+	while (ref) {
+		if (is_master(ref))
+			master_ref = ref;
+		if (head && !memcmp(ref->sha1, head->sha1, 20)) {
+			if (!head_ptr || ref == master_ref)
+				head_ptr = ref;
+		}
+		write_one_ref(ref);
+		ref = ref->next;
+	}
+	if (!head)
+		return;
+
+	head_path = git_path("HEAD");
+	if (!head_ptr) {
+		/*
+		 * If we had a master ref, and it wasn't HEAD, we need to undo the
+		 * symlink, and write a standalone HEAD. Give a warning, because that's
+		 * really really wrong.
+		 */
+		if (master_ref) {
+			error("HEAD doesn't point to any refs! Making standalone HEAD");
+			unlink(head_path);
+		}
+		write_one_ref(head);
+		return;
+	}
+
+	/* We reset to the master branch if it's available */
+	if (master_ref)
+		return;
+
+	/*
+	 * Uhhuh. Other end didn't have master. We start HEAD off with
+	 * the first branch with the same value.
+	 */
+	unlink(head_path);
+	if (symlink(head_ptr->name, head_path) < 0)
+		die("unable to link HEAD to %s", head_ptr->name);
+}
+
+static int clone_pack(int fd[2], int nr_match, char **match)
+{
+	struct ref *refs;
+	int status;
+	pid_t pid;
+
+	refs = get_remote_refs(fd[0], nr_match, match);
+	if (!refs) {
+		packet_flush(fd[1]);
+		die("no matching remote head");
+	}
+	clone_handshake(fd, refs);
+	pid = fork();
+	if (pid < 0)
+		die("git-clone-pack: unable to fork off git-unpack-objects");
+	if (!pid) {
+		close(fd[1]);
+		dup2(fd[0], 0);
+		close(fd[0]);
+		execlp("git-unpack-objects", "git-unpack-objects", NULL);
+		die("git-unpack-objects exec failed");
+	}
+	close(fd[0]);
+	close(fd[1]);
+	while (waitpid(pid, &status, 0) < 0) {
+		if (errno != EINTR)
+			die("waiting for git-unpack-objects: %s", strerror(errno));
+	}
+	if (WIFEXITED(status)) {
+		int code = WEXITSTATUS(status);
+		if (code)
+			die("git-unpack-objects died with error code %d", code);
+		write_refs(refs);
+		return 0;
+	}
+	if (WIFSIGNALED(status)) {
+		int sig = WTERMSIG(status);
+		die("git-unpack-objects died of signal %d", sig);
+	}
+	die("Sherlock Holmes! git-unpack-objects died of unnatural causes %d!", status);
+}
+
+int main(int argc, char **argv)
+{
+	int i, ret, nr_heads;
+	char *dest = NULL, **heads;
+	int fd[2];
+	pid_t pid;
+
+	nr_heads = 0;
+	heads = NULL;
+	for (i = 1; i < argc; i++) {
+		char *arg = argv[i];
+
+		if (*arg == '-') {
+			/* Arguments go here */
+			usage(clone_pack_usage);
+		}
+		dest = arg;
+		heads = argv + i + 1;
+		nr_heads = argc - i - 1;
+		break;
+	}
+	if (!dest)
+		usage(clone_pack_usage);
+	pid = git_connect(fd, dest, exec);
+	if (pid < 0)
+		return 1;
+	ret = clone_pack(fd, nr_heads, heads);
+	close(fd[0]);
+	close(fd[1]);
+	finish_connect(pid);
+	return ret;
+}