Add git-bundle: move objects and references by archive

Some workflows require use of repositories on machines that cannot be
connected, preventing use of git-fetch / git-push to transport objects and
references between the repositories.

git-bundle provides an alternate transport mechanism, effectively allowing
git-fetch and git-pull to operate using sneakernet transport. `git-bundle
create` allows the user to create a bundle containing one or more branches
or tags, but with specified basis assumed to exist on the target
repository. At the receiving end, git-bundle acts like git-fetch-pack,
allowing the user to invoke git-fetch or git-pull using the bundle file as
the URL. git-fetch and git-ls-remote determine they have a bundle URL by
checking that the URL points to a file, but are otherwise unchanged in
operation with bundles.

The original patch was done by Mark Levedahl <mdl123@verizon.net>.

It was updated to make git-bundle a builtin, and get rid of the tar
format: now, the first line is supposed to say "# v2 git bundle", the next
lines either contain a prerequisite ("-" followed by the hash of the
needed commit), or a ref (the hash of a commit, followed by the name of
the ref), and finally the pack. As a result, the bundle argument can be
"-" now.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 389 insertions, 0 deletions

diff --git a/builtin-bundle.c b/builtin-bundle.c
new file mode 100644
index 0000000000..4bd596ab26
--- /dev/null
+++ b/builtin-bundle.c
@@ -0,0 +1,389 @@
+#include "cache.h"
+#include "object.h"
+#include "commit.h"
+#include "diff.h"
+#include "revision.h"
+#include "list-objects.h"
+#include "exec_cmd.h"
+
+/*
+ * Basic handler for bundle files to connect repositories via sneakernet.
+ * Invocation must include action.
+ * This function can create a bundle or provide information on an existing
+ * bundle supporting git-fetch, git-pull, and git-ls-remote
+ */
+
+static const char *bundle_usage="git-bundle (--create <bundle> <git-rev-list args> | --verify <bundle> | --list-heads <bundle> [refname]... | --unbundle <bundle> [refname]... )";
+
+static const char bundle_signature[] = "# v2 git bundle\n";
+
+struct ref_list {
+	unsigned int nr, alloc;
+	struct {
+		unsigned char sha1[20];
+		char *name;
+	} *list;
+};
+
+static void add_to_ref_list(const unsigned char *sha1, const char *name,
+		struct ref_list *list)
+{
+	if (list->nr + 1 >= list->alloc) {
+		list->alloc = alloc_nr(list->nr + 1);
+		list->list = xrealloc(list->list,
+				list->alloc * sizeof(list->list[0]));
+	}
+	memcpy(list->list[list->nr].sha1, sha1, 20);
+	list->list[list->nr].name = xstrdup(name);
+	list->nr++;
+}
+
+struct bundle_header {
+	struct ref_list prerequisites, references;
+};
+
+/* this function returns the length of the string */
+static int read_string(int fd, char *buffer, int size)
+{
+	int i;
+	for (i = 0; i < size - 1; i++) {
+		int count = read(fd, buffer + i, 1);
+		if (count < 0)
+			return error("Read error: %s", strerror(errno));
+		if (count == 0) {
+			i--;
+			break;
+		}
+		if (buffer[i] == '\n')
+			break;
+	}
+	buffer[i + 1] = '\0';
+	return i + 1;
+}
+
+/* returns an fd */
+static int read_header(const char *path, struct bundle_header *header) {
+	char buffer[1024];
+	int fd = open(path, O_RDONLY);
+
+	if (fd < 0)
+		return error("could not open '%s'", path);
+	if (read_string(fd, buffer, sizeof(buffer)) < 0 ||
+			strcmp(buffer, bundle_signature)) {
+		close(fd);
+		return error("'%s' does not look like a v2 bundle file", path);
+	}
+	while (read_string(fd, buffer, sizeof(buffer)) > 0
+			&& buffer[0] != '\n') {
+		int offset = buffer[0] == '-' ? 1 : 0;
+		int len = strlen(buffer);
+		unsigned char sha1[20];
+		struct ref_list *list = offset ? &header->prerequisites
+			: &header->references;
+		if (get_sha1_hex(buffer + offset, sha1)) {
+			close(fd);
+			return error("invalid SHA1: %s", buffer);
+		}
+		if (buffer[len - 1] == '\n')
+			buffer[len - 1] = '\0';
+		add_to_ref_list(sha1, buffer + 41 + offset, list);
+	}
+	return fd;
+}
+
+/* if in && *in >= 0, take that as input file descriptor instead */
+static int fork_with_pipe(const char **argv, int *in, int *out)
+{
+	int needs_in, needs_out;
+	int fdin[2], fdout[2], pid;
+
+	needs_in = in && *in < 0;
+	if (needs_in) {
+		if (pipe(fdin) < 0)
+			return error("could not setup pipe");
+		*in = fdin[1];
+	}
+
+	needs_out = out && *out < 0;
+	if (needs_out) {
+		if (pipe(fdout) < 0)
+			return error("could not setup pipe");
+		*out = fdout[0];
+	}
+
+	if ((pid = fork()) < 0) {
+		if (needs_in) {
+			close(fdin[0]);
+			close(fdin[1]);
+		}
+		if (needs_out) {
+			close(fdout[0]);
+			close(fdout[1]);
+		}
+		return error("could not fork");
+	}
+	if (!pid) {
+		if (needs_in) {
+			dup2(fdin[0], 0);
+			close(fdin[0]);
+			close(fdin[1]);
+		} else if (in)
+			dup2(*in, 0);
+		if (needs_out) {
+			dup2(fdout[1], 1);
+			close(fdout[0]);
+			close(fdout[1]);
+		} else if (out)
+			dup2(*out, 1);
+		exit(execv_git_cmd(argv));
+	}
+	if (needs_in)
+		close(fdin[0]);
+	if (needs_out)
+		close(fdout[1]);
+	return pid;
+}
+
+static int verify_bundle(struct bundle_header *header)
+{
+	/*
+	 * Do fast check, then if any prereqs are missing then go line by line
+	 * to be verbose about the errors
+	 */
+	struct ref_list *p = &header->prerequisites;
+	const char *argv[5] = {"rev-list", "--stdin", "--not", "--all", NULL};
+	int pid, in, out, i, ret = 0;
+	char buffer[1024];
+
+	in = out = -1;
+	pid = fork_with_pipe(argv, &in, &out);
+	if (pid < 0)
+		return error("Could not fork rev-list");
+	if (!fork()) {
+		for (i = 0; i < p->nr; i++) {
+			write(in, sha1_to_hex(p->list[i].sha1), 40);
+			write(in, "\n", 1);
+		}
+		close(in);
+		exit(0);
+	}
+	close(in);
+	while (read_string(out, buffer, sizeof(buffer)) > 0) {
+		if (ret++ == 0)
+			error ("The bundle requires the following commits you lack:");
+		fprintf(stderr, "%s", buffer);
+	}
+	close(out);
+	while (waitpid(pid, &i, 0) < 0)
+		if (errno != EINTR)
+			return -1;
+	if (!ret && (!WIFEXITED(i) || WEXITSTATUS(i)))
+		return error("At least one prerequisite is lacking.");
+
+	return ret;
+}
+
+static int list_heads(struct bundle_header *header, int argc, const char **argv)
+{
+	int i;
+	struct ref_list *r = &header->references;
+
+	for (i = 0; i < r->nr; i++) {
+		if (argc > 1) {
+			int j;
+			for (j = 1; j < argc; j++)
+				if (!strcmp(r->list[i].name, argv[j]))
+					break;
+			if (j == argc)
+				continue;
+		}
+		printf("%s %s\n", sha1_to_hex(r->list[i].sha1),
+				r->list[i].name);
+	}
+	return 0;
+}
+
+static void show_commit(struct commit *commit)
+{
+	write(1, sha1_to_hex(commit->object.sha1), 40);
+	write(1, "\n", 1);
+	if (commit->parents) {
+		free_commit_list(commit->parents);
+		commit->parents = NULL;
+	}
+}
+
+static void show_object(struct object_array_entry *p)
+{
+	/* An object with name "foo\n0000000..." can be used to
+	 *          * confuse downstream git-pack-objects very badly.
+	 *                   */
+	const char *ep = strchr(p->name, '\n');
+	int len = ep ? ep - p->name : strlen(p->name);
+	write(1, sha1_to_hex(p->item->sha1), 40);
+	write(1, " ", 1);
+	if (len)
+		write(1, p->name, len);
+	write(1, "\n", 1);
+}
+
+static int create_bundle(struct bundle_header *header, const char *path,
+		int argc, const char **argv)
+{
+	int bundle_fd = -1;
+	const char **argv_boundary = xmalloc((argc + 3) * sizeof(const char *));
+	const char **argv_pack = xmalloc(4 * sizeof(const char *));
+	int pid, in, out, i, status;
+	char buffer[1024];
+	struct rev_info revs;
+
+	bundle_fd = (!strcmp(path, "-") ? 1 :
+			open(path, O_CREAT | O_WRONLY, 0666));
+	if (bundle_fd < 0)
+		return error("Could not write to '%s'", path);
+
+	/* write signature */
+	write(bundle_fd, bundle_signature, strlen(bundle_signature));
+
+	/* write prerequisites */
+	memcpy(argv_boundary + 2, argv + 1, argc * sizeof(const char *));
+	argv_boundary[0] = "rev-list";
+	argv_boundary[1] = "--boundary";
+	argv_boundary[argc + 1] = NULL;
+	out = -1;
+	pid = fork_with_pipe(argv_boundary, NULL, &out);
+	if (pid < 0)
+		return -1;
+	while ((i = read_string(out, buffer, sizeof(buffer))) > 0)
+		if (buffer[0] == '-')
+			write(bundle_fd, buffer, i);
+	while ((i = waitpid(pid, &status, 0)) < 0)
+		if (errno != EINTR)
+			return error("rev-list died");
+	if (!WIFEXITED(status) || WEXITSTATUS(status))
+		return error("rev-list died %d", WEXITSTATUS(status));
+
+	/* write references */
+	save_commit_buffer = 0;
+	init_revisions(&revs, NULL);
+	revs.tag_objects = 1;
+	revs.tree_objects = 1;
+	revs.blob_objects = 1;
+	argc = setup_revisions(argc, argv, &revs, NULL);
+	if (argc > 1)
+		return error("unrecognized argument: %s'", argv[1]);
+	for (i = 0; i < revs.pending.nr; i++) {
+		struct object_array_entry *e = revs.pending.objects + i;
+		if (!(e->item->flags & UNINTERESTING)) {
+			unsigned char sha1[20];
+			char *ref;
+			if (dwim_ref(e->name, strlen(e->name), sha1, &ref) != 1)
+				continue;
+			write(bundle_fd, sha1_to_hex(e->item->sha1), 40);
+			write(bundle_fd, " ", 1);
+			write(bundle_fd, ref, strlen(ref));
+			write(bundle_fd, "\n", 1);
+			free(ref);
+		}
+	}
+
+	/* end header */
+	write(bundle_fd, "\n", 1);
+
+	/* write pack */
+	argv_pack[0] = "pack-objects";
+	argv_pack[1] = "--all-progress";
+	argv_pack[2] = "--stdout";
+	argv_pack[3] = NULL;
+	in = -1;
+	out = bundle_fd;
+	pid = fork_with_pipe(argv_pack, &in, &out);
+	if (pid < 0)
+		return error("Could not spawn pack-objects");
+	close(1);
+	close(bundle_fd);
+	dup2(in, 1);
+	close(in);
+	prepare_revision_walk(&revs);
+	traverse_commit_list(&revs, show_commit, show_object);
+	close(1);
+	while (waitpid(pid, &status, 0) < 0)
+		if (errno != EINTR)
+			return -1;
+	if (!WIFEXITED(status) || WEXITSTATUS(status))
+		return error ("pack-objects died");
+	return 0;
+}
+
+static int unbundle(struct bundle_header *header, int bundle_fd,
+		int argc, const char **argv)
+{
+	const char *argv_index_pack[] = {"index-pack", "--stdin", NULL};
+	int pid, status, dev_null;
+
+	if (verify_bundle(header))
+		return -1;
+	dev_null = open("/dev/null", O_WRONLY);
+	pid = fork_with_pipe(argv_index_pack, &bundle_fd, &dev_null);
+	if (pid < 0)
+		return error("Could not spawn index-pack");
+	close(bundle_fd);
+	while (waitpid(pid, &status, 0) < 0)
+		if (errno != EINTR)
+			return error("index-pack died");
+	if (!WIFEXITED(status) || WEXITSTATUS(status))
+		return error("index-pack exited with status %d",
+				WEXITSTATUS(status));
+	return list_heads(header, argc, argv);
+}
+
+int cmd_bundle(int argc, const char **argv, const char *prefix)
+{
+	struct bundle_header header;
+	int nongit = 0;
+	const char *cmd, *bundle_file;
+	int bundle_fd = -1;
+	char buffer[PATH_MAX];
+
+	if (argc < 3)
+		usage(bundle_usage);
+
+	cmd = argv[1];
+	bundle_file = argv[2];
+	argc -= 2;
+	argv += 2;
+
+	prefix = setup_git_directory_gently(&nongit);
+	if (prefix && bundle_file[0] != '/') {
+		snprintf(buffer, sizeof(buffer), "%s/%s", prefix, bundle_file);
+		bundle_file = buffer;
+	}
+
+	memset(&header, 0, sizeof(header));
+	if (strcmp(cmd, "create") &&
+			!(bundle_fd = read_header(bundle_file, &header)))
+		return 1;
+
+	if (!strcmp(cmd, "verify")) {
+		close(bundle_fd);
+		if (verify_bundle(&header))
+			return 1;
+		fprintf(stderr, "%s is okay\n", bundle_file);
+		return 0;
+	}
+	if (!strcmp(cmd, "list-heads")) {
+		close(bundle_fd);
+		return !!list_heads(&header, argc, argv);
+	}
+	if (!strcmp(cmd, "create")) {
+		if (nongit)
+			die("Need a repository to create a bundle.");
+		return !!create_bundle(&header, bundle_file, argc, argv);
+	} else if (!strcmp(cmd, "unbundle")) {
+		if (nongit)
+			die("Need a repository to unbundle.");
+		return !!unbundle(&header, bundle_fd, argc, argv);
+	} else
+		usage(bundle_usage);
+}
+