[PATCH 09/16] subtree: rewrite incoming commits

From

Nguyễn Thái Ngọc Duy <pclouds@gmail.com>

Date

Jul 31, 2010, 16:18 UTC

Message-ID

<1280593105-22015-10-git-send-email-pclouds@gmail.com>

In-Reply-To

<1280593105-22015-1-git-send-email-pclouds@gmail.com>

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 subtree.c |  244 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 subtree.h |    1 +
 2 files changed, 245 insertions(+), 0 deletions(-)

diff --git a/subtree.c b/subtree.c
index 601d827..8c075be 100644
--- a/subtree.c
+++ b/subtree.c
@@ -115,3 +115,247 @@ const unsigned char *subtree_lookup_object(const unsigned char *sha1)
 		return subtree_commit[pos]->sha1[1];
 	return sha1;
 }
+
+static unsigned long do_compress(void **pptr, unsigned long size)
+{
+	z_stream stream;
+	void *in, *out;
+	unsigned long maxsize;
+
+	memset(&stream, 0, sizeof(stream));
+	deflateInit(&stream, Z_DEFAULT_COMPRESSION);
+	maxsize = deflateBound(&stream, size);
+
+	in = *pptr;
+	out = xmalloc(maxsize);
+	*pptr = out;
+
+	stream.next_in = in;
+	stream.avail_in = size;
+	stream.next_out = out;
+	stream.avail_out = maxsize;
+	while (deflate(&stream, Z_FINISH) == Z_OK)
+		; /* nothing */
+	deflateEnd(&stream);
+
+	return stream.total_out;
+}
+
+static int nr_written;
+static int add_sha1_to_pack(int fd, void *buf, unsigned long size, enum object_type type)
+{
+	unsigned long datalen;
+	unsigned hdrlen;
+	unsigned char header[10];
+
+	datalen = do_compress(&buf, size);
+	hdrlen = encode_in_pack_object_header(type, size, header);
+	write(fd, header, hdrlen);
+	write(fd, buf, datalen);
+	nr_written++;
+	free(buf);
+	return 0;
+}
+
+/*
+ * Take sha1 of a tree, rewrite it to only return the prefix and return
+ * the newsha1.
+ *
+ * If if is zero, write to object store. If fd is greater than zero,
+ * it's a pack file handle.
+ */
+static int narrow_tree(const unsigned char *sha1, unsigned char *newsha1,
+		       const char *prefix, int fd)
+{
+	struct tree_desc desc;
+	struct name_entry entry;
+	struct strbuf buffer;
+	const char *slash;
+	int subtree_len;
+	enum object_type type;
+	unsigned long size;
+	char *tree;
+	struct object *obj;
+
+	slash = strchr(prefix, '/');
+	subtree_len = slash ? slash - prefix : strlen(prefix);
+
+	tree = read_sha1_file(sha1, &type, &size);
+	if (type != OBJ_TREE)
+		die("%s is not a tree", sha1_to_hex(sha1));
+
+	init_tree_desc(&desc, tree, size);
+	strbuf_init(&buffer, 1024);
+	while (tree_entry(&desc, &entry)) {
+		if (!S_ISDIR(entry.mode))
+			continue;
+
+		if (subtree_len == strlen(entry.path) &&
+		    !strncmp(entry.path, prefix, subtree_len)) {
+			unsigned char newtree_sha1[20];
+
+			if (slash && slash[1]) /* trailing slash does not count */
+				narrow_tree(entry.sha1, newtree_sha1, prefix+subtree_len+1, fd);
+			else
+				memcpy(newtree_sha1, entry.sha1, 20);
+
+			strbuf_addf(&buffer, "%o %.*s%c", entry.mode, strlen(entry.path), entry.path, '\0');
+			strbuf_add(&buffer, newtree_sha1, 20);
+			break;
+		}
+	}
+	free(tree);
+
+	if (fd == 0) {
+		if (write_sha1_file(buffer.buf, buffer.len, tree_type, newsha1)) {
+			error("Could not write replaced tree for %s", sha1_to_hex(sha1));
+			strbuf_release(&buffer);
+			return 1;
+		}
+		strbuf_release(&buffer);
+		return 0;
+	}
+
+	hash_sha1_file(buffer.buf, buffer.len, tree_type, newsha1);
+	obj = (struct object *)lookup_tree(newsha1);
+	if (fd > 0 &&
+	    !(obj->flags & SEEN) &&
+	    add_sha1_to_pack(fd, buffer.buf, buffer.len, OBJ_TREE)) {
+		error("Could not write replaced tree for %s", sha1_to_hex(sha1));
+		strbuf_release(&buffer);
+		return 1;
+	}
+	obj->flags |= SEEN;
+
+	strbuf_release(&buffer);
+	return 0;
+}
+
+/*
+ * Take sha1 of a commit, rewrite its tree using narrow_tree(), then
+ * add a replace entry to file pointer fp (which is $GIT_DIR/subtree).
+ *
+ * Also update replace-object database so that the given sha1 can be
+ * replaced with the new one right after this function returns.
+ */
+static int shadow_commit(const unsigned char *sha1, const char *prefix, int fd, FILE *fp)
+{
+	unsigned char newsha1[20], treesha1[20];
+	enum object_type type;
+	unsigned long size;
+	void *buffer;
+	struct object *obj;
+	int saved_read_replace_refs = read_replace_refs;
+
+	read_replace_refs = 0;
+	buffer = read_sha1_file(sha1, &type, &size);
+	read_replace_refs = saved_read_replace_refs;
+	get_sha1_hex(buffer+5, treesha1);
+
+	if (!buffer || type != OBJ_COMMIT ||
+	    narrow_tree(treesha1, newsha1, prefix, fd)) {
+		free(buffer);
+		error("Failed to narrow tree for commit %s", sha1_to_hex(sha1));
+		return 1;
+	}
+
+	/* replace new tree in */
+	memcpy((char*)buffer+5, sha1_to_hex(newsha1), 40);
+
+	if (fd == 0) {
+		if (write_sha1_file(buffer, size, commit_type, newsha1)) {
+			free(buffer);
+			error("Could not write replaced commit for %s", sha1_to_hex(sha1));
+			return 1;
+		}
+	}
+	else {
+		hash_sha1_file(buffer, size, commit_type, newsha1);
+		obj = (struct object *)lookup_commit(newsha1);
+		if (fd > 0 &&
+		    !(obj->flags & SEEN) &&
+		    add_sha1_to_pack(fd, buffer, size, OBJ_COMMIT)) {
+			free(buffer);
+			error("Could not write replaced commit for %s", sha1_to_hex(sha1));
+			return 1;
+		}
+		obj->flags |= SEEN;
+	}
+
+	if (fp) {
+		char buf[82];
+		memcpy(buf, sha1_to_hex(sha1), 40);
+		buf[40] = ' ';
+		memcpy(buf+41, sha1_to_hex(newsha1), 40);
+		buf[81] = '\n';
+		fwrite(buf, 82, 1, fp);
+	}
+	free(buffer);
+
+	return 0;
+}
+
+/*
+ * Rewrite all reachable commits in repo using shadow_commit().
+ * Write out the pack that contains new tree/commit objects.
+ */
+void subtree_import()
+{
+	const char *args[] = {"rev-list", "--all", NULL};
+	struct pack_header hdr;
+	struct progress *ps;
+	struct rev_info revs;
+	struct commit *c;
+	unsigned char sha1[20];
+	unsigned commit_nr = 0;
+	char *pack_tmp_name;
+	char tmpname[PATH_MAX];
+	int pack_fd, i;
+	FILE *fp;
+	char cmd[1024];
+
+	/* Packing */
+	init_revisions(&revs, NULL);
+	setup_revisions(2, args, &revs, NULL);
+	if (prepare_revision_walk(&revs))
+		die("revision walk setup failed");
+	fp = fopen(git_path("subtree"), "w+");
+
+	pack_fd = odb_mkstemp(tmpname, sizeof(tmpname), "pack/tmp_pack_XXXXXX");
+	pack_tmp_name = xstrdup(tmpname);
+
+	hdr.hdr_signature = htonl(PACK_SIGNATURE);
+	hdr.hdr_version = htonl(PACK_VERSION);
+	hdr.hdr_entries = htonl(0);
+	write(pack_fd, &hdr, sizeof(hdr));
+
+	ps = start_progress("Preparing subtree commits", 0);
+	while ((c = get_revision(&revs)) != NULL) {
+		if (shadow_commit(c->object.sha1, core_subtree, pack_fd, fp))
+			die("Failed to shadow commit %s", c->object.sha1);
+		display_progress(ps, ++commit_nr);
+	}
+	stop_progress(&ps);
+	fclose(fp);
+	fixup_pack_header_footer(pack_fd, sha1, pack_tmp_name, nr_written, NULL, 0);
+	close(pack_fd);
+	sprintf(cmd, "git index-pack --stdin < %s", pack_tmp_name);
+	system(cmd);
+	unlink(pack_tmp_name);
+
+	reprepare_packed_git();
+	if (subtree_commit)
+		free(subtree_commit);
+	prepare_subtree_commit();
+
+	/* Invalidate all replaced commits */
+	for (i = 0; i < subtree_commit_nr; i++) {
+		/* lookup_commit() would create new objects, we don't want that */
+		c = (struct commit *)lookup_object(subtree_commit[i]->sha1[0]);
+		if (c)
+			invalidate_commit(c);
+	}
+
+	if (revs.pending.nr)
+		free(revs.pending.objects);
+}
diff --git a/subtree.h b/subtree.h
index 157153a..3512e2a 100644
--- a/subtree.h
+++ b/subtree.h
@@ -1,2 +1,3 @@
 void prepare_subtree_commit();
 const unsigned char *subtree_lookup_object(const unsigned char *sha1);
+void subtree_import();

-- 
1.7.1.rc1.69.g24c2f7