Add 'git fast-export', the sister of 'git fast-import'

This program dumps (parts of) a git repository in the format that
fast-import understands.

For clarity's sake, it does not use the 'inline' method of specifying
blobs in the commits, but builds the blobs before building the commits.

Since signed tags' signatures will not necessarily be valid (think
transformations after the export, or excluding revisions, changing
the history), there are 4 modes to handle them: abort (default),
ignore, warn and strip.  The latter just turns the tags into
unsigned ones.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 406 insertions, 0 deletions

diff --git a/builtin-fast-export.c b/builtin-fast-export.c
new file mode 100755
index 000000000..72be45db4
--- /dev/null
+++ b/builtin-fast-export.c
@@ -0,0 +1,406 @@
+/*
+ * "git fast-export" builtin command
+ *
+ * Copyright (C) 2007 Johannes E. Schindelin
+ */
+#include "builtin.h"
+#include "cache.h"
+#include "commit.h"
+#include "object.h"
+#include "tag.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "log-tree.h"
+#include "revision.h"
+#include "decorate.h"
+#include "path-list.h"
+#include "utf8.h"
+#include "parse-options.h"
+
+static const char *fast_export_usage[] = {
+	"git-fast-export [rev-list-opts]",
+	NULL
+};
+
+static int progress;
+static enum { IGNORE, WARN, STRIP, ABORT } signed_tag_mode = ABORT;
+
+static int parse_opt_signed_tag_mode(const struct option *opt,
+				     const char *arg, int unset)
+{
+	if (unset || !strcmp(arg, "abort"))
+		signed_tag_mode = ABORT;
+	else if (!strcmp(arg, "ignore"))
+		signed_tag_mode = IGNORE;
+	else if (!strcmp(arg, "warn"))
+		signed_tag_mode = WARN;
+	else if (!strcmp(arg, "strip"))
+		signed_tag_mode = STRIP;
+	else
+		return error("Unknown signed-tag mode: %s", arg);
+	return 0;
+}
+
+static struct decoration idnums;
+static uint32_t last_idnum;
+
+static int has_unshown_parent(struct commit *commit)
+{
+	struct commit_list *parent;
+
+	for (parent = commit->parents; parent; parent = parent->next)
+		if (!(parent->item->object.flags & SHOWN) &&
+		    !(parent->item->object.flags & UNINTERESTING))
+			return 1;
+	return 0;
+}
+
+/* Since intptr_t is C99, we do not use it here */
+static void mark_object(struct object *object)
+{
+	last_idnum++;
+	add_decoration(&idnums, object, ((uint32_t *)NULL) + last_idnum);
+}
+
+static int get_object_mark(struct object *object)
+{
+	void *decoration = lookup_decoration(&idnums, object);
+	if (!decoration)
+		return 0;
+	return (uint32_t *)decoration - (uint32_t *)NULL;
+}
+
+static void show_progress(void)
+{
+	static int counter = 0;
+	if (!progress)
+		return;
+	if ((++counter % progress) == 0)
+		printf("progress %d objects\n", counter);
+}
+
+static void handle_object(const unsigned char *sha1)
+{
+	unsigned long size;
+	enum object_type type;
+	char *buf;
+	struct object *object;
+
+	if (is_null_sha1(sha1))
+		return;
+
+	object = parse_object(sha1);
+	if (!object)
+		die ("Could not read blob %s", sha1_to_hex(sha1));
+
+	if (object->flags & SHOWN)
+		return;
+
+	buf = read_sha1_file(sha1, &type, &size);
+	if (!buf)
+		die ("Could not read blob %s", sha1_to_hex(sha1));
+
+	mark_object(object);
+
+	printf("blob\nmark :%d\ndata %lu\n", last_idnum, size);
+	if (fwrite(buf, size, 1, stdout) != 1)
+		die ("Could not write blob %s", sha1_to_hex(sha1));
+	printf("\n");
+
+	show_progress();
+
+	object->flags |= SHOWN;
+	free(buf);
+}
+
+static void show_filemodify(struct diff_queue_struct *q,
+			    struct diff_options *options, void *data)
+{
+	int i;
+	for (i = 0; i < q->nr; i++) {
+		struct diff_filespec *spec = q->queue[i]->two;
+		if (is_null_sha1(spec->sha1))
+			printf("D %s\n", spec->path);
+		else {
+			struct object *object = lookup_object(spec->sha1);
+			printf("M 0%06o :%d %s\n", spec->mode,
+			       get_object_mark(object), spec->path);
+		}
+	}
+}
+
+static const char *find_encoding(const char *begin, const char *end)
+{
+	const char *needle = "\nencoding ";
+	char *bol, *eol;
+
+	bol = memmem(begin, end ? end - begin : strlen(begin),
+		     needle, strlen(needle));
+	if (!bol)
+		return git_commit_encoding;
+	bol += strlen(needle);
+	eol = strchrnul(bol, '\n');
+	*eol = '\0';
+	return bol;
+}
+
+static void handle_commit(struct commit *commit, struct rev_info *rev)
+{
+	int saved_output_format = rev->diffopt.output_format;
+	const char *author, *author_end, *committer, *committer_end;
+	const char *encoding, *message;
+	char *reencoded = NULL;
+	struct commit_list *p;
+	int i;
+
+	rev->diffopt.output_format = DIFF_FORMAT_CALLBACK;
+
+	parse_commit(commit);
+	author = strstr(commit->buffer, "\nauthor ");
+	if (!author)
+		die ("Could not find author in commit %s",
+		     sha1_to_hex(commit->object.sha1));
+	author++;
+	author_end = strchrnul(author, '\n');
+	committer = strstr(author_end, "\ncommitter ");
+	if (!committer)
+		die ("Could not find committer in commit %s",
+		     sha1_to_hex(commit->object.sha1));
+	committer++;
+	committer_end = strchrnul(committer, '\n');
+	message = strstr(committer_end, "\n\n");
+	encoding = find_encoding(committer_end, message);
+	if (message)
+		message += 2;
+
+	if (commit->parents) {
+		parse_commit(commit->parents->item);
+		diff_tree_sha1(commit->parents->item->tree->object.sha1,
+			       commit->tree->object.sha1, "", &rev->diffopt);
+	}
+	else
+		diff_root_tree_sha1(commit->tree->object.sha1,
+				    "", &rev->diffopt);
+
+	for (i = 0; i < diff_queued_diff.nr; i++)
+		handle_object(diff_queued_diff.queue[i]->two->sha1);
+
+	mark_object(&commit->object);
+	if (!is_encoding_utf8(encoding))
+		reencoded = reencode_string(message, "UTF-8", encoding);
+	printf("commit %s\nmark :%d\n%.*s\n%.*s\ndata %u\n%s",
+	       (const char *)commit->util, last_idnum,
+	       (int)(author_end - author), author,
+	       (int)(committer_end - committer), committer,
+	       (unsigned)(reencoded
+			  ? strlen(reencoded) : message
+			  ? strlen(message) : 0),
+	       reencoded ? reencoded : message ? message : "");
+	if (reencoded)
+		free(reencoded);
+
+	for (i = 0, p = commit->parents; p; p = p->next) {
+		int mark = get_object_mark(&p->item->object);
+		if (!mark)
+			continue;
+		if (i == 0)
+			printf("from :%d\n", mark);
+		else if (i == 1)
+			printf("merge :%d", mark);
+		else
+			printf(" :%d", mark);
+		i++;
+	}
+	if (i > 1)
+		printf("\n");
+
+	log_tree_diff_flush(rev);
+	rev->diffopt.output_format = saved_output_format;
+
+	printf("\n");
+
+	show_progress();
+}
+
+static void handle_tail(struct object_array *commits, struct rev_info *revs)
+{
+	struct commit *commit;
+	while (commits->nr) {
+		commit = (struct commit *)commits->objects[commits->nr - 1].item;
+		if (has_unshown_parent(commit))
+			return;
+		handle_commit(commit, revs);
+		commits->nr--;
+	}
+}
+
+static void handle_tag(const char *name, struct tag *tag)
+{
+	unsigned long size;
+	enum object_type type;
+	char *buf;
+	const char *tagger, *tagger_end, *message;
+	size_t message_size = 0;
+
+	buf = read_sha1_file(tag->object.sha1, &type, &size);
+	if (!buf)
+		die ("Could not read tag %s", sha1_to_hex(tag->object.sha1));
+	message = memmem(buf, size, "\n\n", 2);
+	if (message) {
+		message += 2;
+		message_size = strlen(message);
+	}
+	tagger = memmem(buf, message ? message - buf : size, "\ntagger ", 8);
+	if (!tagger)
+		die ("No tagger for tag %s", sha1_to_hex(tag->object.sha1));
+	tagger++;
+	tagger_end = strchrnul(tagger, '\n');
+
+	/* handle signed tags */
+	if (message) {
+		const char *signature = strstr(message,
+					       "\n-----BEGIN PGP SIGNATURE-----\n");
+		if (signature)
+			switch(signed_tag_mode) {
+			case ABORT:
+				die ("Encountered signed tag %s; use "
+				     "--signed-tag=<mode> to handle it.",
+				     sha1_to_hex(tag->object.sha1));
+			case WARN:
+				warning ("Exporting signed tag %s",
+					 sha1_to_hex(tag->object.sha1));
+				/* fallthru */
+			case IGNORE:
+				break;
+			case STRIP:
+				message_size = signature + 1 - message;
+				break;
+			}
+	}
+
+	if (!prefixcmp(name, "refs/tags/"))
+		name += 10;
+	printf("tag %s\nfrom :%d\n%.*s\ndata %d\n%.*s\n",
+	       name, get_object_mark(tag->tagged),
+	       (int)(tagger_end - tagger), tagger,
+	       (int)message_size, (int)message_size, message ? message : "");
+}
+
+static void get_tags_and_duplicates(struct object_array *pending,
+				    struct path_list *extra_refs)
+{
+	struct tag *tag;
+	int i;
+
+	for (i = 0; i < pending->nr; i++) {
+		struct object_array_entry *e = pending->objects + i;
+		unsigned char sha1[20];
+		struct commit *commit = commit;
+		char *full_name;
+
+		if (dwim_ref(e->name, strlen(e->name), sha1, &full_name) != 1)
+			continue;
+
+		switch (e->item->type) {
+		case OBJ_COMMIT:
+			commit = (struct commit *)e->item;
+			break;
+		case OBJ_TAG:
+			tag = (struct tag *)e->item;
+			while (tag && tag->object.type == OBJ_TAG) {
+				path_list_insert(full_name, extra_refs)->util = tag;
+				tag = (struct tag *)tag->tagged;
+			}
+			if (!tag)
+				die ("Tag %s points nowhere?", e->name);
+			switch(tag->object.type) {
+			case OBJ_COMMIT:
+				commit = (struct commit *)tag;
+				break;
+			case OBJ_BLOB:
+				handle_object(tag->object.sha1);
+				continue;
+			}
+			break;
+		default:
+			die ("Unexpected object of type %s",
+			     typename(e->item->type));
+		}
+		if (commit->util)
+			/* more than one name for the same object */
+			path_list_insert(full_name, extra_refs)->util = commit;
+		else
+			commit->util = full_name;
+	}
+}
+
+static void handle_tags_and_duplicates(struct path_list *extra_refs)
+{
+	struct commit *commit;
+	int i;
+
+	for (i = extra_refs->nr - 1; i >= 0; i--) {
+		const char *name = extra_refs->items[i].path;
+		struct object *object = extra_refs->items[i].util;
+		switch (object->type) {
+		case OBJ_TAG:
+			handle_tag(name, (struct tag *)object);
+			break;
+		case OBJ_COMMIT:
+			/* create refs pointing to already seen commits */
+			commit = (struct commit *)object;
+			printf("reset %s\nfrom :%d\n\n", name,
+			       get_object_mark(&commit->object));
+			show_progress();
+			break;
+		}
+	}
+}
+
+int cmd_fast_export(int argc, const char **argv, const char *prefix)
+{
+	struct rev_info revs;
+	struct object_array commits = { 0, 0, NULL };
+	struct path_list extra_refs = { NULL, 0, 0, 0 };
+	struct commit *commit;
+	struct option options[] = {
+		OPT_INTEGER(0, "progress", &progress,
+			    "show progress after <n> objects"),
+		OPT_CALLBACK(0, "signed-tags", &signed_tag_mode, "mode",
+			     "select handling of signed tags",
+			     parse_opt_signed_tag_mode),
+		OPT_END()
+	};
+
+	/* we handle encodings */
+	git_config(git_default_config);
+
+	init_revisions(&revs, prefix);
+	argc = setup_revisions(argc, argv, &revs, NULL);
+	argc = parse_options(argc, argv, options, fast_export_usage, 0);
+	if (argc > 1)
+		usage_with_options (fast_export_usage, options);
+
+	get_tags_and_duplicates(&revs.pending, &extra_refs);
+
+	prepare_revision_walk(&revs);
+	revs.diffopt.format_callback = show_filemodify;
+	DIFF_OPT_SET(&revs.diffopt, RECURSIVE);
+	while ((commit = get_revision(&revs))) {
+		if (has_unshown_parent(commit)) {
+			struct commit_list *parent = commit->parents;
+			add_object_array(&commit->object, NULL, &commits);
+			for (; parent; parent = parent->next)
+				if (!parent->item->util)
+					parent->item->util = commit->util;
+		}
+		else {
+			handle_commit(commit, &revs);
+			handle_tail(&commits, &revs);
+		}
+	}
+
+	handle_tags_and_duplicates(&extra_refs);
+
+	return 0;
+}