merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

Merge commit '1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5' as 'third_party/git'

1 files changed, 2161 insertions, 0 deletions

diff --git a/third_party/git/packfile.c b/third_party/git/packfile.c
new file mode 100644
index 000000000000..fc43a6c52c75
--- /dev/null
+++ b/third_party/git/packfile.c
@@ -0,0 +1,2161 @@
+#include "cache.h"
+#include "list.h"
+#include "pack.h"
+#include "repository.h"
+#include "dir.h"
+#include "mergesort.h"
+#include "packfile.h"
+#include "delta.h"
+#include "list.h"
+#include "streaming.h"
+#include "sha1-lookup.h"
+#include "commit.h"
+#include "object.h"
+#include "tag.h"
+#include "tree-walk.h"
+#include "tree.h"
+#include "object-store.h"
+#include "midx.h"
+#include "commit-graph.h"
+
+char *odb_pack_name(struct strbuf *buf,
+		    const unsigned char *sha1,
+		    const char *ext)
+{
+	strbuf_reset(buf);
+	strbuf_addf(buf, "%s/pack/pack-%s.%s", get_object_directory(),
+		    sha1_to_hex(sha1), ext);
+	return buf->buf;
+}
+
+char *sha1_pack_name(const unsigned char *sha1)
+{
+	static struct strbuf buf = STRBUF_INIT;
+	return odb_pack_name(&buf, sha1, "pack");
+}
+
+char *sha1_pack_index_name(const unsigned char *sha1)
+{
+	static struct strbuf buf = STRBUF_INIT;
+	return odb_pack_name(&buf, sha1, "idx");
+}
+
+static unsigned int pack_used_ctr;
+static unsigned int pack_mmap_calls;
+static unsigned int peak_pack_open_windows;
+static unsigned int pack_open_windows;
+static unsigned int pack_open_fds;
+static unsigned int pack_max_fds;
+static size_t peak_pack_mapped;
+static size_t pack_mapped;
+
+#define SZ_FMT PRIuMAX
+static inline uintmax_t sz_fmt(size_t s) { return s; }
+
+void pack_report(void)
+{
+	fprintf(stderr,
+		"pack_report: getpagesize()            = %10" SZ_FMT "\n"
+		"pack_report: core.packedGitWindowSize = %10" SZ_FMT "\n"
+		"pack_report: core.packedGitLimit      = %10" SZ_FMT "\n",
+		sz_fmt(getpagesize()),
+		sz_fmt(packed_git_window_size),
+		sz_fmt(packed_git_limit));
+	fprintf(stderr,
+		"pack_report: pack_used_ctr            = %10u\n"
+		"pack_report: pack_mmap_calls          = %10u\n"
+		"pack_report: pack_open_windows        = %10u / %10u\n"
+		"pack_report: pack_mapped              = "
+			"%10" SZ_FMT " / %10" SZ_FMT "\n",
+		pack_used_ctr,
+		pack_mmap_calls,
+		pack_open_windows, peak_pack_open_windows,
+		sz_fmt(pack_mapped), sz_fmt(peak_pack_mapped));
+}
+
+/*
+ * Open and mmap the index file at path, perform a couple of
+ * consistency checks, then record its information to p.  Return 0 on
+ * success.
+ */
+static int check_packed_git_idx(const char *path, struct packed_git *p)
+{
+	void *idx_map;
+	size_t idx_size;
+	int fd = git_open(path), ret;
+	struct stat st;
+	const unsigned int hashsz = the_hash_algo->rawsz;
+
+	if (fd < 0)
+		return -1;
+	if (fstat(fd, &st)) {
+		close(fd);
+		return -1;
+	}
+	idx_size = xsize_t(st.st_size);
+	if (idx_size < 4 * 256 + hashsz + hashsz) {
+		close(fd);
+		return error("index file %s is too small", path);
+	}
+	idx_map = xmmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	close(fd);
+
+	ret = load_idx(path, hashsz, idx_map, idx_size, p);
+
+	if (ret)
+		munmap(idx_map, idx_size);
+
+	return ret;
+}
+
+int load_idx(const char *path, const unsigned int hashsz, void *idx_map,
+	     size_t idx_size, struct packed_git *p)
+{
+	struct pack_idx_header *hdr = idx_map;
+	uint32_t version, nr, i, *index;
+
+	if (idx_size < 4 * 256 + hashsz + hashsz)
+		return error("index file %s is too small", path);
+	if (idx_map == NULL)
+		return error("empty data");
+
+	if (hdr->idx_signature == htonl(PACK_IDX_SIGNATURE)) {
+		version = ntohl(hdr->idx_version);
+		if (version < 2 || version > 2)
+			return error("index file %s is version %"PRIu32
+				     " and is not supported by this binary"
+				     " (try upgrading GIT to a newer version)",
+				     path, version);
+	} else
+		version = 1;
+
+	nr = 0;
+	index = idx_map;
+	if (version > 1)
+		index += 2;  /* skip index header */
+	for (i = 0; i < 256; i++) {
+		uint32_t n = ntohl(index[i]);
+		if (n < nr)
+			return error("non-monotonic index %s", path);
+		nr = n;
+	}
+
+	if (version == 1) {
+		/*
+		 * Total size:
+		 *  - 256 index entries 4 bytes each
+		 *  - 24-byte entries * nr (object ID + 4-byte offset)
+		 *  - hash of the packfile
+		 *  - file checksum
+		 */
+		if (idx_size != 4 * 256 + nr * (hashsz + 4) + hashsz + hashsz)
+			return error("wrong index v1 file size in %s", path);
+	} else if (version == 2) {
+		/*
+		 * Minimum size:
+		 *  - 8 bytes of header
+		 *  - 256 index entries 4 bytes each
+		 *  - object ID entry * nr
+		 *  - 4-byte crc entry * nr
+		 *  - 4-byte offset entry * nr
+		 *  - hash of the packfile
+		 *  - file checksum
+		 * And after the 4-byte offset table might be a
+		 * variable sized table containing 8-byte entries
+		 * for offsets larger than 2^31.
+		 */
+		unsigned long min_size = 8 + 4*256 + nr*(hashsz + 4 + 4) + hashsz + hashsz;
+		unsigned long max_size = min_size;
+		if (nr)
+			max_size += (nr - 1)*8;
+		if (idx_size < min_size || idx_size > max_size)
+			return error("wrong index v2 file size in %s", path);
+		if (idx_size != min_size &&
+		    /*
+		     * make sure we can deal with large pack offsets.
+		     * 31-bit signed offset won't be enough, neither
+		     * 32-bit unsigned one will be.
+		     */
+		    (sizeof(off_t) <= 4))
+			return error("pack too large for current definition of off_t in %s", path);
+	}
+
+	p->index_version = version;
+	p->index_data = idx_map;
+	p->index_size = idx_size;
+	p->num_objects = nr;
+	return 0;
+}
+
+int open_pack_index(struct packed_git *p)
+{
+	char *idx_name;
+	size_t len;
+	int ret;
+
+	if (p->index_data)
+		return 0;
+
+	if (!strip_suffix(p->pack_name, ".pack", &len))
+		BUG("pack_name does not end in .pack");
+	idx_name = xstrfmt("%.*s.idx", (int)len, p->pack_name);
+	ret = check_packed_git_idx(idx_name, p);
+	free(idx_name);
+	return ret;
+}
+
+uint32_t get_pack_fanout(struct packed_git *p, uint32_t value)
+{
+	const uint32_t *level1_ofs = p->index_data;
+
+	if (!level1_ofs) {
+		if (open_pack_index(p))
+			return 0;
+		level1_ofs = p->index_data;
+	}
+
+	if (p->index_version > 1) {
+		level1_ofs += 2;
+	}
+
+	return ntohl(level1_ofs[value]);
+}
+
+static struct packed_git *alloc_packed_git(int extra)
+{
+	struct packed_git *p = xmalloc(st_add(sizeof(*p), extra));
+	memset(p, 0, sizeof(*p));
+	p->pack_fd = -1;
+	return p;
+}
+
+struct packed_git *parse_pack_index(unsigned char *sha1, const char *idx_path)
+{
+	const char *path = sha1_pack_name(sha1);
+	size_t alloc = st_add(strlen(path), 1);
+	struct packed_git *p = alloc_packed_git(alloc);
+
+	memcpy(p->pack_name, path, alloc); /* includes NUL */
+	hashcpy(p->hash, sha1);
+	if (check_packed_git_idx(idx_path, p)) {
+		free(p);
+		return NULL;
+	}
+
+	return p;
+}
+
+static void scan_windows(struct packed_git *p,
+	struct packed_git **lru_p,
+	struct pack_window **lru_w,
+	struct pack_window **lru_l)
+{
+	struct pack_window *w, *w_l;
+
+	for (w_l = NULL, w = p->windows; w; w = w->next) {
+		if (!w->inuse_cnt) {
+			if (!*lru_w || w->last_used < (*lru_w)->last_used) {
+				*lru_p = p;
+				*lru_w = w;
+				*lru_l = w_l;
+			}
+		}
+		w_l = w;
+	}
+}
+
+static int unuse_one_window(struct packed_git *current)
+{
+	struct packed_git *p, *lru_p = NULL;
+	struct pack_window *lru_w = NULL, *lru_l = NULL;
+
+	if (current)
+		scan_windows(current, &lru_p, &lru_w, &lru_l);
+	for (p = the_repository->objects->packed_git; p; p = p->next)
+		scan_windows(p, &lru_p, &lru_w, &lru_l);
+	if (lru_p) {
+		munmap(lru_w->base, lru_w->len);
+		pack_mapped -= lru_w->len;
+		if (lru_l)
+			lru_l->next = lru_w->next;
+		else
+			lru_p->windows = lru_w->next;
+		free(lru_w);
+		pack_open_windows--;
+		return 1;
+	}
+	return 0;
+}
+
+void release_pack_memory(size_t need)
+{
+	size_t cur = pack_mapped;
+	while (need >= (cur - pack_mapped) && unuse_one_window(NULL))
+		; /* nothing */
+}
+
+void close_pack_windows(struct packed_git *p)
+{
+	while (p->windows) {
+		struct pack_window *w = p->windows;
+
+		if (w->inuse_cnt)
+			die("pack '%s' still has open windows to it",
+			    p->pack_name);
+		munmap(w->base, w->len);
+		pack_mapped -= w->len;
+		pack_open_windows--;
+		p->windows = w->next;
+		free(w);
+	}
+}
+
+int close_pack_fd(struct packed_git *p)
+{
+	if (p->pack_fd < 0)
+		return 0;
+
+	close(p->pack_fd);
+	pack_open_fds--;
+	p->pack_fd = -1;
+
+	return 1;
+}
+
+void close_pack_index(struct packed_git *p)
+{
+	if (p->index_data) {
+		munmap((void *)p->index_data, p->index_size);
+		p->index_data = NULL;
+	}
+}
+
+void close_pack(struct packed_git *p)
+{
+	close_pack_windows(p);
+	close_pack_fd(p);
+	close_pack_index(p);
+}
+
+void close_object_store(struct raw_object_store *o)
+{
+	struct packed_git *p;
+
+	for (p = o->packed_git; p; p = p->next)
+		if (p->do_not_close)
+			BUG("want to close pack marked 'do-not-close'");
+		else
+			close_pack(p);
+
+	if (o->multi_pack_index) {
+		close_midx(o->multi_pack_index);
+		o->multi_pack_index = NULL;
+	}
+
+	close_commit_graph(o);
+}
+
+void unlink_pack_path(const char *pack_name, int force_delete)
+{
+	static const char *exts[] = {".pack", ".idx", ".keep", ".bitmap", ".promisor"};
+	int i;
+	struct strbuf buf = STRBUF_INIT;
+	size_t plen;
+
+	strbuf_addstr(&buf, pack_name);
+	strip_suffix_mem(buf.buf, &buf.len, ".pack");
+	plen = buf.len;
+
+	if (!force_delete) {
+		strbuf_addstr(&buf, ".keep");
+		if (!access(buf.buf, F_OK)) {
+			strbuf_release(&buf);
+			return;
+		}
+	}
+
+	for (i = 0; i < ARRAY_SIZE(exts); i++) {
+		strbuf_setlen(&buf, plen);
+		strbuf_addstr(&buf, exts[i]);
+		unlink(buf.buf);
+	}
+
+	strbuf_release(&buf);
+}
+
+/*
+ * The LRU pack is the one with the oldest MRU window, preferring packs
+ * with no used windows, or the oldest mtime if it has no windows allocated.
+ */
+static void find_lru_pack(struct packed_git *p, struct packed_git **lru_p, struct pack_window **mru_w, int *accept_windows_inuse)
+{
+	struct pack_window *w, *this_mru_w;
+	int has_windows_inuse = 0;
+
+	/*
+	 * Reject this pack if it has windows and the previously selected
+	 * one does not.  If this pack does not have windows, reject
+	 * it if the pack file is newer than the previously selected one.
+	 */
+	if (*lru_p && !*mru_w && (p->windows || p->mtime > (*lru_p)->mtime))
+		return;
+
+	for (w = this_mru_w = p->windows; w; w = w->next) {
+		/*
+		 * Reject this pack if any of its windows are in use,
+		 * but the previously selected pack did not have any
+		 * inuse windows.  Otherwise, record that this pack
+		 * has windows in use.
+		 */
+		if (w->inuse_cnt) {
+			if (*accept_windows_inuse)
+				has_windows_inuse = 1;
+			else
+				return;
+		}
+
+		if (w->last_used > this_mru_w->last_used)
+			this_mru_w = w;
+
+		/*
+		 * Reject this pack if it has windows that have been
+		 * used more recently than the previously selected pack.
+		 * If the previously selected pack had windows inuse and
+		 * we have not encountered a window in this pack that is
+		 * inuse, skip this check since we prefer a pack with no
+		 * inuse windows to one that has inuse windows.
+		 */
+		if (*mru_w && *accept_windows_inuse == has_windows_inuse &&
+		    this_mru_w->last_used > (*mru_w)->last_used)
+			return;
+	}
+
+	/*
+	 * Select this pack.
+	 */
+	*mru_w = this_mru_w;
+	*lru_p = p;
+	*accept_windows_inuse = has_windows_inuse;
+}
+
+static int close_one_pack(void)
+{
+	struct packed_git *p, *lru_p = NULL;
+	struct pack_window *mru_w = NULL;
+	int accept_windows_inuse = 1;
+
+	for (p = the_repository->objects->packed_git; p; p = p->next) {
+		if (p->pack_fd == -1)
+			continue;
+		find_lru_pack(p, &lru_p, &mru_w, &accept_windows_inuse);
+	}
+
+	if (lru_p)
+		return close_pack_fd(lru_p);
+
+	return 0;
+}
+
+static unsigned int get_max_fd_limit(void)
+{
+#ifdef RLIMIT_NOFILE
+	{
+		struct rlimit lim;
+
+		if (!getrlimit(RLIMIT_NOFILE, &lim))
+			return lim.rlim_cur;
+	}
+#endif
+
+#ifdef _SC_OPEN_MAX
+	{
+		long open_max = sysconf(_SC_OPEN_MAX);
+		if (0 < open_max)
+			return open_max;
+		/*
+		 * Otherwise, we got -1 for one of the two
+		 * reasons:
+		 *
+		 * (1) sysconf() did not understand _SC_OPEN_MAX
+		 *     and signaled an error with -1; or
+		 * (2) sysconf() said there is no limit.
+		 *
+		 * We _could_ clear errno before calling sysconf() to
+		 * tell these two cases apart and return a huge number
+		 * in the latter case to let the caller cap it to a
+		 * value that is not so selfish, but letting the
+		 * fallback OPEN_MAX codepath take care of these cases
+		 * is a lot simpler.
+		 */
+	}
+#endif
+
+#ifdef OPEN_MAX
+	return OPEN_MAX;
+#else
+	return 1; /* see the caller ;-) */
+#endif
+}
+
+const char *pack_basename(struct packed_git *p)
+{
+	const char *ret = strrchr(p->pack_name, '/');
+	if (ret)
+		ret = ret + 1; /* skip past slash */
+	else
+		ret = p->pack_name; /* we only have a base */
+	return ret;
+}
+
+/*
+ * Do not call this directly as this leaks p->pack_fd on error return;
+ * call open_packed_git() instead.
+ */
+static int open_packed_git_1(struct packed_git *p)
+{
+	struct stat st;
+	struct pack_header hdr;
+	unsigned char hash[GIT_MAX_RAWSZ];
+	unsigned char *idx_hash;
+	long fd_flag;
+	ssize_t read_result;
+	const unsigned hashsz = the_hash_algo->rawsz;
+
+	if (!p->index_data) {
+		struct multi_pack_index *m;
+		const char *pack_name = pack_basename(p);
+
+		for (m = the_repository->objects->multi_pack_index;
+		     m; m = m->next) {
+			if (midx_contains_pack(m, pack_name))
+				break;
+		}
+
+		if (!m && open_pack_index(p))
+			return error("packfile %s index unavailable", p->pack_name);
+	}
+
+	if (!pack_max_fds) {
+		unsigned int max_fds = get_max_fd_limit();
+
+		/* Save 3 for stdin/stdout/stderr, 22 for work */
+		if (25 < max_fds)
+			pack_max_fds = max_fds - 25;
+		else
+			pack_max_fds = 1;
+	}
+
+	while (pack_max_fds <= pack_open_fds && close_one_pack())
+		; /* nothing */
+
+	p->pack_fd = git_open(p->pack_name);
+	if (p->pack_fd < 0 || fstat(p->pack_fd, &st))
+		return -1;
+	pack_open_fds++;
+
+	/* If we created the struct before we had the pack we lack size. */
+	if (!p->pack_size) {
+		if (!S_ISREG(st.st_mode))
+			return error("packfile %s not a regular file", p->pack_name);
+		p->pack_size = st.st_size;
+	} else if (p->pack_size != st.st_size)
+		return error("packfile %s size changed", p->pack_name);
+
+	/* We leave these file descriptors open with sliding mmap;
+	 * there is no point keeping them open across exec(), though.
+	 */
+	fd_flag = fcntl(p->pack_fd, F_GETFD, 0);
+	if (fd_flag < 0)
+		return error("cannot determine file descriptor flags");
+	fd_flag |= FD_CLOEXEC;
+	if (fcntl(p->pack_fd, F_SETFD, fd_flag) == -1)
+		return error("cannot set FD_CLOEXEC");
+
+	/* Verify we recognize this pack file format. */
+	read_result = read_in_full(p->pack_fd, &hdr, sizeof(hdr));
+	if (read_result < 0)
+		return error_errno("error reading from %s", p->pack_name);
+	if (read_result != sizeof(hdr))
+		return error("file %s is far too short to be a packfile", p->pack_name);
+	if (hdr.hdr_signature != htonl(PACK_SIGNATURE))
+		return error("file %s is not a GIT packfile", p->pack_name);
+	if (!pack_version_ok(hdr.hdr_version))
+		return error("packfile %s is version %"PRIu32" and not"
+			" supported (try upgrading GIT to a newer version)",
+			p->pack_name, ntohl(hdr.hdr_version));
+
+	/* Skip index checking if in multi-pack-index */
+	if (!p->index_data)
+		return 0;
+
+	/* Verify the pack matches its index. */
+	if (p->num_objects != ntohl(hdr.hdr_entries))
+		return error("packfile %s claims to have %"PRIu32" objects"
+			     " while index indicates %"PRIu32" objects",
+			     p->pack_name, ntohl(hdr.hdr_entries),
+			     p->num_objects);
+	if (lseek(p->pack_fd, p->pack_size - hashsz, SEEK_SET) == -1)
+		return error("end of packfile %s is unavailable", p->pack_name);
+	read_result = read_in_full(p->pack_fd, hash, hashsz);
+	if (read_result < 0)
+		return error_errno("error reading from %s", p->pack_name);
+	if (read_result != hashsz)
+		return error("packfile %s signature is unavailable", p->pack_name);
+	idx_hash = ((unsigned char *)p->index_data) + p->index_size - hashsz * 2;
+	if (!hasheq(hash, idx_hash))
+		return error("packfile %s does not match index", p->pack_name);
+	return 0;
+}
+
+static int open_packed_git(struct packed_git *p)
+{
+	if (!open_packed_git_1(p))
+		return 0;
+	close_pack_fd(p);
+	return -1;
+}
+
+static int in_window(struct pack_window *win, off_t offset)
+{
+	/* We must promise at least one full hash after the
+	 * offset is available from this window, otherwise the offset
+	 * is not actually in this window and a different window (which
+	 * has that one hash excess) must be used.  This is to support
+	 * the object header and delta base parsing routines below.
+	 */
+	off_t win_off = win->offset;
+	return win_off <= offset
+		&& (offset + the_hash_algo->rawsz) <= (win_off + win->len);
+}
+
+unsigned char *use_pack(struct packed_git *p,
+		struct pack_window **w_cursor,
+		off_t offset,
+		unsigned long *left)
+{
+	struct pack_window *win = *w_cursor;
+
+	/* Since packfiles end in a hash of their content and it's
+	 * pointless to ask for an offset into the middle of that
+	 * hash, and the in_window function above wouldn't match
+	 * don't allow an offset too close to the end of the file.
+	 */
+	if (!p->pack_size && p->pack_fd == -1 && open_packed_git(p))
+		die("packfile %s cannot be accessed", p->pack_name);
+	if (offset > (p->pack_size - the_hash_algo->rawsz))
+		die("offset beyond end of packfile (truncated pack?)");
+	if (offset < 0)
+		die(_("offset before end of packfile (broken .idx?)"));
+
+	if (!win || !in_window(win, offset)) {
+		if (win)
+			win->inuse_cnt--;
+		for (win = p->windows; win; win = win->next) {
+			if (in_window(win, offset))
+				break;
+		}
+		if (!win) {
+			size_t window_align = packed_git_window_size / 2;
+			off_t len;
+
+			if (p->pack_fd == -1 && open_packed_git(p))
+				die("packfile %s cannot be accessed", p->pack_name);
+
+			win = xcalloc(1, sizeof(*win));
+			win->offset = (offset / window_align) * window_align;
+			len = p->pack_size - win->offset;
+			if (len > packed_git_window_size)
+				len = packed_git_window_size;
+			win->len = (size_t)len;
+			pack_mapped += win->len;
+			while (packed_git_limit < pack_mapped
+				&& unuse_one_window(p))
+				; /* nothing */
+			win->base = xmmap_gently(NULL, win->len,
+				PROT_READ, MAP_PRIVATE,
+				p->pack_fd, win->offset);
+			if (win->base == MAP_FAILED)
+				die_errno("packfile %s cannot be mapped",
+					  p->pack_name);
+			if (!win->offset && win->len == p->pack_size
+				&& !p->do_not_close)
+				close_pack_fd(p);
+			pack_mmap_calls++;
+			pack_open_windows++;
+			if (pack_mapped > peak_pack_mapped)
+				peak_pack_mapped = pack_mapped;
+			if (pack_open_windows > peak_pack_open_windows)
+				peak_pack_open_windows = pack_open_windows;
+			win->next = p->windows;
+			p->windows = win;
+		}
+	}
+	if (win != *w_cursor) {
+		win->last_used = pack_used_ctr++;
+		win->inuse_cnt++;
+		*w_cursor = win;
+	}
+	offset -= win->offset;
+	if (left)
+		*left = win->len - xsize_t(offset);
+	return win->base + offset;
+}
+
+void unuse_pack(struct pack_window **w_cursor)
+{
+	struct pack_window *w = *w_cursor;
+	if (w) {
+		w->inuse_cnt--;
+		*w_cursor = NULL;
+	}
+}
+
+static void try_to_free_pack_memory(size_t size)
+{
+	release_pack_memory(size);
+}
+
+struct packed_git *add_packed_git(const char *path, size_t path_len, int local)
+{
+	static int have_set_try_to_free_routine;
+	struct stat st;
+	size_t alloc;
+	struct packed_git *p;
+
+	if (!have_set_try_to_free_routine) {
+		have_set_try_to_free_routine = 1;
+		set_try_to_free_routine(try_to_free_pack_memory);
+	}
+
+	/*
+	 * Make sure a corresponding .pack file exists and that
+	 * the index looks sane.
+	 */
+	if (!strip_suffix_mem(path, &path_len, ".idx"))
+		return NULL;
+
+	/*
+	 * ".promisor" is long enough to hold any suffix we're adding (and
+	 * the use xsnprintf double-checks that)
+	 */
+	alloc = st_add3(path_len, strlen(".promisor"), 1);
+	p = alloc_packed_git(alloc);
+	memcpy(p->pack_name, path, path_len);
+
+	xsnprintf(p->pack_name + path_len, alloc - path_len, ".keep");
+	if (!access(p->pack_name, F_OK))
+		p->pack_keep = 1;
+
+	xsnprintf(p->pack_name + path_len, alloc - path_len, ".promisor");
+	if (!access(p->pack_name, F_OK))
+		p->pack_promisor = 1;
+
+	xsnprintf(p->pack_name + path_len, alloc - path_len, ".pack");
+	if (stat(p->pack_name, &st) || !S_ISREG(st.st_mode)) {
+		free(p);
+		return NULL;
+	}
+
+	/* ok, it looks sane as far as we can check without
+	 * actually mapping the pack file.
+	 */
+	p->pack_size = st.st_size;
+	p->pack_local = local;
+	p->mtime = st.st_mtime;
+	if (path_len < the_hash_algo->hexsz ||
+	    get_sha1_hex(path + path_len - the_hash_algo->hexsz, p->hash))
+		hashclr(p->hash);
+	return p;
+}
+
+void install_packed_git(struct repository *r, struct packed_git *pack)
+{
+	if (pack->pack_fd != -1)
+		pack_open_fds++;
+
+	pack->next = r->objects->packed_git;
+	r->objects->packed_git = pack;
+}
+
+void (*report_garbage)(unsigned seen_bits, const char *path);
+
+static void report_helper(const struct string_list *list,
+			  int seen_bits, int first, int last)
+{
+	if (seen_bits == (PACKDIR_FILE_PACK|PACKDIR_FILE_IDX))
+		return;
+
+	for (; first < last; first++)
+		report_garbage(seen_bits, list->items[first].string);
+}
+
+static void report_pack_garbage(struct string_list *list)
+{
+	int i, baselen = -1, first = 0, seen_bits = 0;
+
+	if (!report_garbage)
+		return;
+
+	string_list_sort(list);
+
+	for (i = 0; i < list->nr; i++) {
+		const char *path = list->items[i].string;
+		if (baselen != -1 &&
+		    strncmp(path, list->items[first].string, baselen)) {
+			report_helper(list, seen_bits, first, i);
+			baselen = -1;
+			seen_bits = 0;
+		}
+		if (baselen == -1) {
+			const char *dot = strrchr(path, '.');
+			if (!dot) {
+				report_garbage(PACKDIR_FILE_GARBAGE, path);
+				continue;
+			}
+			baselen = dot - path + 1;
+			first = i;
+		}
+		if (!strcmp(path + baselen, "pack"))
+			seen_bits |= 1;
+		else if (!strcmp(path + baselen, "idx"))
+			seen_bits |= 2;
+	}
+	report_helper(list, seen_bits, first, list->nr);
+}
+
+void for_each_file_in_pack_dir(const char *objdir,
+			       each_file_in_pack_dir_fn fn,
+			       void *data)
+{
+	struct strbuf path = STRBUF_INIT;
+	size_t dirnamelen;
+	DIR *dir;
+	struct dirent *de;
+
+	strbuf_addstr(&path, objdir);
+	strbuf_addstr(&path, "/pack");
+	dir = opendir(path.buf);
+	if (!dir) {
+		if (errno != ENOENT)
+			error_errno("unable to open object pack directory: %s",
+				    path.buf);
+		strbuf_release(&path);
+		return;
+	}
+	strbuf_addch(&path, '/');
+	dirnamelen = path.len;
+	while ((de = readdir(dir)) != NULL) {
+		if (is_dot_or_dotdot(de->d_name))
+			continue;
+
+		strbuf_setlen(&path, dirnamelen);
+		strbuf_addstr(&path, de->d_name);
+
+		fn(path.buf, path.len, de->d_name, data);
+	}
+
+	closedir(dir);
+	strbuf_release(&path);
+}
+
+struct prepare_pack_data {
+	struct repository *r;
+	struct string_list *garbage;
+	int local;
+	struct multi_pack_index *m;
+};
+
+static void prepare_pack(const char *full_name, size_t full_name_len,
+			 const char *file_name, void *_data)
+{
+	struct prepare_pack_data *data = (struct prepare_pack_data *)_data;
+	struct packed_git *p;
+	size_t base_len = full_name_len;
+
+	if (strip_suffix_mem(full_name, &base_len, ".idx") &&
+	    !(data->m && midx_contains_pack(data->m, file_name))) {
+		/* Don't reopen a pack we already have. */
+		for (p = data->r->objects->packed_git; p; p = p->next) {
+			size_t len;
+			if (strip_suffix(p->pack_name, ".pack", &len) &&
+			    len == base_len &&
+			    !memcmp(p->pack_name, full_name, len))
+				break;
+		}
+
+		if (!p) {
+			p = add_packed_git(full_name, full_name_len, data->local);
+			if (p)
+				install_packed_git(data->r, p);
+		}
+	}
+
+	if (!report_garbage)
+		return;
+
+	if (!strcmp(file_name, "multi-pack-index"))
+		return;
+	if (ends_with(file_name, ".idx") ||
+	    ends_with(file_name, ".pack") ||
+	    ends_with(file_name, ".bitmap") ||
+	    ends_with(file_name, ".keep") ||
+	    ends_with(file_name, ".promisor"))
+		string_list_append(data->garbage, full_name);
+	else
+		report_garbage(PACKDIR_FILE_GARBAGE, full_name);
+}
+
+static void prepare_packed_git_one(struct repository *r, char *objdir, int local)
+{
+	struct prepare_pack_data data;
+	struct string_list garbage = STRING_LIST_INIT_DUP;
+
+	data.m = r->objects->multi_pack_index;
+
+	/* look for the multi-pack-index for this object directory */
+	while (data.m && strcmp(data.m->object_dir, objdir))
+		data.m = data.m->next;
+
+	data.r = r;
+	data.garbage = &garbage;
+	data.local = local;
+
+	for_each_file_in_pack_dir(objdir, prepare_pack, &data);
+
+	report_pack_garbage(data.garbage);
+	string_list_clear(data.garbage, 0);
+}
+
+static void prepare_packed_git(struct repository *r);
+/*
+ * Give a fast, rough count of the number of objects in the repository. This
+ * ignores loose objects completely. If you have a lot of them, then either
+ * you should repack because your performance will be awful, or they are
+ * all unreachable objects about to be pruned, in which case they're not really
+ * interesting as a measure of repo size in the first place.
+ */
+unsigned long repo_approximate_object_count(struct repository *r)
+{
+	if (!r->objects->approximate_object_count_valid) {
+		unsigned long count;
+		struct multi_pack_index *m;
+		struct packed_git *p;
+
+		prepare_packed_git(r);
+		count = 0;
+		for (m = get_multi_pack_index(r); m; m = m->next)
+			count += m->num_objects;
+		for (p = r->objects->packed_git; p; p = p->next) {
+			if (open_pack_index(p))
+				continue;
+			count += p->num_objects;
+		}
+		r->objects->approximate_object_count = count;
+	}
+	return r->objects->approximate_object_count;
+}
+
+static void *get_next_packed_git(const void *p)
+{
+	return ((const struct packed_git *)p)->next;
+}
+
+static void set_next_packed_git(void *p, void *next)
+{
+	((struct packed_git *)p)->next = next;
+}
+
+static int sort_pack(const void *a_, const void *b_)
+{
+	const struct packed_git *a = a_;
+	const struct packed_git *b = b_;
+	int st;
+
+	/*
+	 * Local packs tend to contain objects specific to our
+	 * variant of the project than remote ones.  In addition,
+	 * remote ones could be on a network mounted filesystem.
+	 * Favor local ones for these reasons.
+	 */
+	st = a->pack_local - b->pack_local;
+	if (st)
+		return -st;
+
+	/*
+	 * Younger packs tend to contain more recent objects,
+	 * and more recent objects tend to get accessed more
+	 * often.
+	 */
+	if (a->mtime < b->mtime)
+		return 1;
+	else if (a->mtime == b->mtime)
+		return 0;
+	return -1;
+}
+
+static void rearrange_packed_git(struct repository *r)
+{
+	r->objects->packed_git = llist_mergesort(
+		r->objects->packed_git, get_next_packed_git,
+		set_next_packed_git, sort_pack);
+}
+
+static void prepare_packed_git_mru(struct repository *r)
+{
+	struct packed_git *p;
+
+	INIT_LIST_HEAD(&r->objects->packed_git_mru);
+
+	for (p = r->objects->packed_git; p; p = p->next)
+		list_add_tail(&p->mru, &r->objects->packed_git_mru);
+}
+
+static void prepare_packed_git(struct repository *r)
+{
+	struct object_directory *odb;
+
+	if (r->objects->packed_git_initialized)
+		return;
+
+	prepare_alt_odb(r);
+	for (odb = r->objects->odb; odb; odb = odb->next) {
+		int local = (odb == r->objects->odb);
+		prepare_multi_pack_index_one(r, odb->path, local);
+		prepare_packed_git_one(r, odb->path, local);
+	}
+	rearrange_packed_git(r);
+
+	prepare_packed_git_mru(r);
+	r->objects->packed_git_initialized = 1;
+}
+
+void reprepare_packed_git(struct repository *r)
+{
+	struct object_directory *odb;
+
+	for (odb = r->objects->odb; odb; odb = odb->next)
+		odb_clear_loose_cache(odb);
+
+	r->objects->approximate_object_count_valid = 0;
+	r->objects->packed_git_initialized = 0;
+	prepare_packed_git(r);
+}
+
+struct packed_git *get_packed_git(struct repository *r)
+{
+	prepare_packed_git(r);
+	return r->objects->packed_git;
+}
+
+struct multi_pack_index *get_multi_pack_index(struct repository *r)
+{
+	prepare_packed_git(r);
+	return r->objects->multi_pack_index;
+}
+
+struct packed_git *get_all_packs(struct repository *r)
+{
+	struct multi_pack_index *m;
+
+	prepare_packed_git(r);
+	for (m = r->objects->multi_pack_index; m; m = m->next) {
+		uint32_t i;
+		for (i = 0; i < m->num_packs; i++)
+			prepare_midx_pack(r, m, i);
+	}
+
+	return r->objects->packed_git;
+}
+
+struct list_head *get_packed_git_mru(struct repository *r)
+{
+	prepare_packed_git(r);
+	return &r->objects->packed_git_mru;
+}
+
+unsigned long unpack_object_header_buffer(const unsigned char *buf,
+		unsigned long len, enum object_type *type, unsigned long *sizep)
+{
+	unsigned shift;
+	unsigned long size, c;
+	unsigned long used = 0;
+
+	c = buf[used++];
+	*type = (c >> 4) & 7;
+	size = c & 15;
+	shift = 4;
+	while (c & 0x80) {
+		if (len <= used || bitsizeof(long) <= shift) {
+			error("bad object header");
+			size = used = 0;
+			break;
+		}
+		c = buf[used++];
+		size += (c & 0x7f) << shift;
+		shift += 7;
+	}
+	*sizep = size;
+	return used;
+}
+
+unsigned long get_size_from_delta(struct packed_git *p,
+				  struct pack_window **w_curs,
+				  off_t curpos)
+{
+	const unsigned char *data;
+	unsigned char delta_head[20], *in;
+	git_zstream stream;
+	int st;
+
+	memset(&stream, 0, sizeof(stream));
+	stream.next_out = delta_head;
+	stream.avail_out = sizeof(delta_head);
+
+	git_inflate_init(&stream);
+	do {
+		in = use_pack(p, w_curs, curpos, &stream.avail_in);
+		stream.next_in = in;
+		st = git_inflate(&stream, Z_FINISH);
+		curpos += stream.next_in - in;
+	} while ((st == Z_OK || st == Z_BUF_ERROR) &&
+		 stream.total_out < sizeof(delta_head));
+	git_inflate_end(&stream);
+	if ((st != Z_STREAM_END) && stream.total_out != sizeof(delta_head)) {
+		error("delta data unpack-initial failed");
+		return 0;
+	}
+
+	/* Examine the initial part of the delta to figure out
+	 * the result size.
+	 */
+	data = delta_head;
+
+	/* ignore base size */
+	get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
+
+	/* Read the result size */
+	return get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
+}
+
+int unpack_object_header(struct packed_git *p,
+			 struct pack_window **w_curs,
+			 off_t *curpos,
+			 unsigned long *sizep)
+{
+	unsigned char *base;
+	unsigned long left;
+	unsigned long used;
+	enum object_type type;
+
+	/* use_pack() assures us we have [base, base + 20) available
+	 * as a range that we can look at.  (Its actually the hash
+	 * size that is assured.)  With our object header encoding
+	 * the maximum deflated object size is 2^137, which is just
+	 * insane, so we know won't exceed what we have been given.
+	 */
+	base = use_pack(p, w_curs, *curpos, &left);
+	used = unpack_object_header_buffer(base, left, &type, sizep);
+	if (!used) {
+		type = OBJ_BAD;
+	} else
+		*curpos += used;
+
+	return type;
+}
+
+void mark_bad_packed_object(struct packed_git *p, const unsigned char *sha1)
+{
+	unsigned i;
+	const unsigned hashsz = the_hash_algo->rawsz;
+	for (i = 0; i < p->num_bad_objects; i++)
+		if (hasheq(sha1, p->bad_object_sha1 + hashsz * i))
+			return;
+	p->bad_object_sha1 = xrealloc(p->bad_object_sha1,
+				      st_mult(GIT_MAX_RAWSZ,
+					      st_add(p->num_bad_objects, 1)));
+	hashcpy(p->bad_object_sha1 + hashsz * p->num_bad_objects, sha1);
+	p->num_bad_objects++;
+}
+
+const struct packed_git *has_packed_and_bad(struct repository *r,
+					    const unsigned char *sha1)
+{
+	struct packed_git *p;
+	unsigned i;
+
+	for (p = r->objects->packed_git; p; p = p->next)
+		for (i = 0; i < p->num_bad_objects; i++)
+			if (hasheq(sha1,
+				   p->bad_object_sha1 + the_hash_algo->rawsz * i))
+				return p;
+	return NULL;
+}
+
+static off_t get_delta_base(struct packed_git *p,
+				    struct pack_window **w_curs,
+				    off_t *curpos,
+				    enum object_type type,
+				    off_t delta_obj_offset)
+{
+	unsigned char *base_info = use_pack(p, w_curs, *curpos, NULL);
+	off_t base_offset;
+
+	/* use_pack() assured us we have [base_info, base_info + 20)
+	 * as a range that we can look at without walking off the
+	 * end of the mapped window.  Its actually the hash size
+	 * that is assured.  An OFS_DELTA longer than the hash size
+	 * is stupid, as then a REF_DELTA would be smaller to store.
+	 */
+	if (type == OBJ_OFS_DELTA) {
+		unsigned used = 0;
+		unsigned char c = base_info[used++];
+		base_offset = c & 127;
+		while (c & 128) {
+			base_offset += 1;
+			if (!base_offset || MSB(base_offset, 7))
+				return 0;  /* overflow */
+			c = base_info[used++];
+			base_offset = (base_offset << 7) + (c & 127);
+		}
+		base_offset = delta_obj_offset - base_offset;
+		if (base_offset <= 0 || base_offset >= delta_obj_offset)
+			return 0;  /* out of bound */
+		*curpos += used;
+	} else if (type == OBJ_REF_DELTA) {
+		/* The base entry _must_ be in the same pack */
+		base_offset = find_pack_entry_one(base_info, p);
+		*curpos += the_hash_algo->rawsz;
+	} else
+		die("I am totally screwed");
+	return base_offset;
+}
+
+/*
+ * Like get_delta_base above, but we return the sha1 instead of the pack
+ * offset. This means it is cheaper for REF deltas (we do not have to do
+ * the final object lookup), but more expensive for OFS deltas (we
+ * have to load the revidx to convert the offset back into a sha1).
+ */
+static const unsigned char *get_delta_base_sha1(struct packed_git *p,
+						struct pack_window **w_curs,
+						off_t curpos,
+						enum object_type type,
+						off_t delta_obj_offset)
+{
+	if (type == OBJ_REF_DELTA) {
+		unsigned char *base = use_pack(p, w_curs, curpos, NULL);
+		return base;
+	} else if (type == OBJ_OFS_DELTA) {
+		struct revindex_entry *revidx;
+		off_t base_offset = get_delta_base(p, w_curs, &curpos,
+						   type, delta_obj_offset);
+
+		if (!base_offset)
+			return NULL;
+
+		revidx = find_pack_revindex(p, base_offset);
+		if (!revidx)
+			return NULL;
+
+		return nth_packed_object_sha1(p, revidx->nr);
+	} else
+		return NULL;
+}
+
+static int retry_bad_packed_offset(struct repository *r,
+				   struct packed_git *p,
+				   off_t obj_offset)
+{
+	int type;
+	struct revindex_entry *revidx;
+	struct object_id oid;
+	revidx = find_pack_revindex(p, obj_offset);
+	if (!revidx)
+		return OBJ_BAD;
+	nth_packed_object_oid(&oid, p, revidx->nr);
+	mark_bad_packed_object(p, oid.hash);
+	type = oid_object_info(r, &oid, NULL);
+	if (type <= OBJ_NONE)
+		return OBJ_BAD;
+	return type;
+}
+
+#define POI_STACK_PREALLOC 64
+
+static enum object_type packed_to_object_type(struct repository *r,
+					      struct packed_git *p,
+					      off_t obj_offset,
+					      enum object_type type,
+					      struct pack_window **w_curs,
+					      off_t curpos)
+{
+	off_t small_poi_stack[POI_STACK_PREALLOC];
+	off_t *poi_stack = small_poi_stack;
+	int poi_stack_nr = 0, poi_stack_alloc = POI_STACK_PREALLOC;
+
+	while (type == OBJ_OFS_DELTA || type == OBJ_REF_DELTA) {
+		off_t base_offset;
+		unsigned long size;
+		/* Push the object we're going to leave behind */
+		if (poi_stack_nr >= poi_stack_alloc && poi_stack == small_poi_stack) {
+			poi_stack_alloc = alloc_nr(poi_stack_nr);
+			ALLOC_ARRAY(poi_stack, poi_stack_alloc);
+			COPY_ARRAY(poi_stack, small_poi_stack, poi_stack_nr);
+		} else {
+			ALLOC_GROW(poi_stack, poi_stack_nr+1, poi_stack_alloc);
+		}
+		poi_stack[poi_stack_nr++] = obj_offset;
+		/* If parsing the base offset fails, just unwind */
+		base_offset = get_delta_base(p, w_curs, &curpos, type, obj_offset);
+		if (!base_offset)
+			goto unwind;
+		curpos = obj_offset = base_offset;
+		type = unpack_object_header(p, w_curs, &curpos, &size);
+		if (type <= OBJ_NONE) {
+			/* If getting the base itself fails, we first
+			 * retry the base, otherwise unwind */
+			type = retry_bad_packed_offset(r, p, base_offset);
+			if (type > OBJ_NONE)
+				goto out;
+			goto unwind;
+		}
+	}
+
+	switch (type) {
+	case OBJ_BAD:
+	case OBJ_COMMIT:
+	case OBJ_TREE:
+	case OBJ_BLOB:
+	case OBJ_TAG:
+		break;
+	default:
+		error("unknown object type %i at offset %"PRIuMAX" in %s",
+		      type, (uintmax_t)obj_offset, p->pack_name);
+		type = OBJ_BAD;
+	}
+
+out:
+	if (poi_stack != small_poi_stack)
+		free(poi_stack);
+	return type;
+
+unwind:
+	while (poi_stack_nr) {
+		obj_offset = poi_stack[--poi_stack_nr];
+		type = retry_bad_packed_offset(r, p, obj_offset);
+		if (type > OBJ_NONE)
+			goto out;
+	}
+	type = OBJ_BAD;
+	goto out;
+}
+
+static struct hashmap delta_base_cache;
+static size_t delta_base_cached;
+
+static LIST_HEAD(delta_base_cache_lru);
+
+struct delta_base_cache_key {
+	struct packed_git *p;
+	off_t base_offset;
+};
+
+struct delta_base_cache_entry {
+	struct hashmap hash;
+	struct delta_base_cache_key key;
+	struct list_head lru;
+	void *data;
+	unsigned long size;
+	enum object_type type;
+};
+
+static unsigned int pack_entry_hash(struct packed_git *p, off_t base_offset)
+{
+	unsigned int hash;
+
+	hash = (unsigned int)(intptr_t)p + (unsigned int)base_offset;
+	hash += (hash >> 8) + (hash >> 16);
+	return hash;
+}
+
+static struct delta_base_cache_entry *
+get_delta_base_cache_entry(struct packed_git *p, off_t base_offset)
+{
+	struct hashmap_entry entry;
+	struct delta_base_cache_key key;
+
+	if (!delta_base_cache.cmpfn)
+		return NULL;
+
+	hashmap_entry_init(&entry, pack_entry_hash(p, base_offset));
+	key.p = p;
+	key.base_offset = base_offset;
+	return hashmap_get(&delta_base_cache, &entry, &key);
+}
+
+static int delta_base_cache_key_eq(const struct delta_base_cache_key *a,
+				   const struct delta_base_cache_key *b)
+{
+	return a->p == b->p && a->base_offset == b->base_offset;
+}
+
+static int delta_base_cache_hash_cmp(const void *unused_cmp_data,
+				     const void *va, const void *vb,
+				     const void *vkey)
+{
+	const struct delta_base_cache_entry *a = va, *b = vb;
+	const struct delta_base_cache_key *key = vkey;
+	if (key)
+		return !delta_base_cache_key_eq(&a->key, key);
+	else
+		return !delta_base_cache_key_eq(&a->key, &b->key);
+}
+
+static int in_delta_base_cache(struct packed_git *p, off_t base_offset)
+{
+	return !!get_delta_base_cache_entry(p, base_offset);
+}
+
+/*
+ * Remove the entry from the cache, but do _not_ free the associated
+ * entry data. The caller takes ownership of the "data" buffer, and
+ * should copy out any fields it wants before detaching.
+ */
+static void detach_delta_base_cache_entry(struct delta_base_cache_entry *ent)
+{
+	hashmap_remove(&delta_base_cache, ent, &ent->key);
+	list_del(&ent->lru);
+	delta_base_cached -= ent->size;
+	free(ent);
+}
+
+static void *cache_or_unpack_entry(struct repository *r, struct packed_git *p,
+				   off_t base_offset, unsigned long *base_size,
+				   enum object_type *type)
+{
+	struct delta_base_cache_entry *ent;
+
+	ent = get_delta_base_cache_entry(p, base_offset);
+	if (!ent)
+		return unpack_entry(r, p, base_offset, type, base_size);
+
+	if (type)
+		*type = ent->type;
+	if (base_size)
+		*base_size = ent->size;
+	return xmemdupz(ent->data, ent->size);
+}
+
+static inline void release_delta_base_cache(struct delta_base_cache_entry *ent)
+{
+	free(ent->data);
+	detach_delta_base_cache_entry(ent);
+}
+
+void clear_delta_base_cache(void)
+{
+	struct list_head *lru, *tmp;
+	list_for_each_safe(lru, tmp, &delta_base_cache_lru) {
+		struct delta_base_cache_entry *entry =
+			list_entry(lru, struct delta_base_cache_entry, lru);
+		release_delta_base_cache(entry);
+	}
+}
+
+static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
+	void *base, unsigned long base_size, enum object_type type)
+{
+	struct delta_base_cache_entry *ent = xmalloc(sizeof(*ent));
+	struct list_head *lru, *tmp;
+
+	delta_base_cached += base_size;
+
+	list_for_each_safe(lru, tmp, &delta_base_cache_lru) {
+		struct delta_base_cache_entry *f =
+			list_entry(lru, struct delta_base_cache_entry, lru);
+		if (delta_base_cached <= delta_base_cache_limit)
+			break;
+		release_delta_base_cache(f);
+	}
+
+	ent->key.p = p;
+	ent->key.base_offset = base_offset;
+	ent->type = type;
+	ent->data = base;
+	ent->size = base_size;
+	list_add_tail(&ent->lru, &delta_base_cache_lru);
+
+	if (!delta_base_cache.cmpfn)
+		hashmap_init(&delta_base_cache, delta_base_cache_hash_cmp, NULL, 0);
+	hashmap_entry_init(ent, pack_entry_hash(p, base_offset));
+	hashmap_add(&delta_base_cache, ent);
+}
+
+int packed_object_info(struct repository *r, struct packed_git *p,
+		       off_t obj_offset, struct object_info *oi)
+{
+	struct pack_window *w_curs = NULL;
+	unsigned long size;
+	off_t curpos = obj_offset;
+	enum object_type type;
+
+	/*
+	 * We always get the representation type, but only convert it to
+	 * a "real" type later if the caller is interested.
+	 */
+	if (oi->contentp) {
+		*oi->contentp = cache_or_unpack_entry(r, p, obj_offset, oi->sizep,
+						      &type);
+		if (!*oi->contentp)
+			type = OBJ_BAD;
+	} else {
+		type = unpack_object_header(p, &w_curs, &curpos, &size);
+	}
+
+	if (!oi->contentp && oi->sizep) {
+		if (type == OBJ_OFS_DELTA || type == OBJ_REF_DELTA) {
+			off_t tmp_pos = curpos;
+			off_t base_offset = get_delta_base(p, &w_curs, &tmp_pos,
+							   type, obj_offset);
+			if (!base_offset) {
+				type = OBJ_BAD;
+				goto out;
+			}
+			*oi->sizep = get_size_from_delta(p, &w_curs, tmp_pos);
+			if (*oi->sizep == 0) {
+				type = OBJ_BAD;
+				goto out;
+			}
+		} else {
+			*oi->sizep = size;
+		}
+	}
+
+	if (oi->disk_sizep) {
+		struct revindex_entry *revidx = find_pack_revindex(p, obj_offset);
+		*oi->disk_sizep = revidx[1].offset - obj_offset;
+	}
+
+	if (oi->typep || oi->type_name) {
+		enum object_type ptot;
+		ptot = packed_to_object_type(r, p, obj_offset,
+					     type, &w_curs, curpos);
+		if (oi->typep)
+			*oi->typep = ptot;
+		if (oi->type_name) {
+			const char *tn = type_name(ptot);
+			if (tn)
+				strbuf_addstr(oi->type_name, tn);
+		}
+		if (ptot < 0) {
+			type = OBJ_BAD;
+			goto out;
+		}
+	}
+
+	if (oi->delta_base_sha1) {
+		if (type == OBJ_OFS_DELTA || type == OBJ_REF_DELTA) {
+			const unsigned char *base;
+
+			base = get_delta_base_sha1(p, &w_curs, curpos,
+						   type, obj_offset);
+			if (!base) {
+				type = OBJ_BAD;
+				goto out;
+			}
+
+			hashcpy(oi->delta_base_sha1, base);
+		} else
+			hashclr(oi->delta_base_sha1);
+	}
+
+	oi->whence = in_delta_base_cache(p, obj_offset) ? OI_DBCACHED :
+							  OI_PACKED;
+
+out:
+	unuse_pack(&w_curs);
+	return type;
+}
+
+static void *unpack_compressed_entry(struct packed_git *p,
+				    struct pack_window **w_curs,
+				    off_t curpos,
+				    unsigned long size)
+{
+	int st;
+	git_zstream stream;
+	unsigned char *buffer, *in;
+
+	buffer = xmallocz_gently(size);
+	if (!buffer)
+		return NULL;
+	memset(&stream, 0, sizeof(stream));
+	stream.next_out = buffer;
+	stream.avail_out = size + 1;
+
+	git_inflate_init(&stream);
+	do {
+		in = use_pack(p, w_curs, curpos, &stream.avail_in);
+		stream.next_in = in;
+		st = git_inflate(&stream, Z_FINISH);
+		if (!stream.avail_out)
+			break; /* the payload is larger than it should be */
+		curpos += stream.next_in - in;
+	} while (st == Z_OK || st == Z_BUF_ERROR);
+	git_inflate_end(&stream);
+	if ((st != Z_STREAM_END) || stream.total_out != size) {
+		free(buffer);
+		return NULL;
+	}
+
+	/* versions of zlib can clobber unconsumed portion of outbuf */
+	buffer[size] = '\0';
+
+	return buffer;
+}
+
+static void write_pack_access_log(struct packed_git *p, off_t obj_offset)
+{
+	static struct trace_key pack_access = TRACE_KEY_INIT(PACK_ACCESS);
+	trace_printf_key(&pack_access, "%s %"PRIuMAX"\n",
+			 p->pack_name, (uintmax_t)obj_offset);
+}
+
+int do_check_packed_object_crc;
+
+#define UNPACK_ENTRY_STACK_PREALLOC 64
+struct unpack_entry_stack_ent {
+	off_t obj_offset;
+	off_t curpos;
+	unsigned long size;
+};
+
+static void *read_object(struct repository *r,
+			 const struct object_id *oid,
+			 enum object_type *type,
+			 unsigned long *size)
+{
+	struct object_info oi = OBJECT_INFO_INIT;
+	void *content;
+	oi.typep = type;
+	oi.sizep = size;
+	oi.contentp = &content;
+
+	if (oid_object_info_extended(r, oid, &oi, 0) < 0)
+		return NULL;
+	return content;
+}
+
+void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
+		   enum object_type *final_type, unsigned long *final_size)
+{
+	struct pack_window *w_curs = NULL;
+	off_t curpos = obj_offset;
+	void *data = NULL;
+	unsigned long size;
+	enum object_type type;
+	struct unpack_entry_stack_ent small_delta_stack[UNPACK_ENTRY_STACK_PREALLOC];
+	struct unpack_entry_stack_ent *delta_stack = small_delta_stack;
+	int delta_stack_nr = 0, delta_stack_alloc = UNPACK_ENTRY_STACK_PREALLOC;
+	int base_from_cache = 0;
+
+	write_pack_access_log(p, obj_offset);
+
+	/* PHASE 1: drill down to the innermost base object */
+	for (;;) {
+		off_t base_offset;
+		int i;
+		struct delta_base_cache_entry *ent;
+
+		ent = get_delta_base_cache_entry(p, curpos);
+		if (ent) {
+			type = ent->type;
+			data = ent->data;
+			size = ent->size;
+			detach_delta_base_cache_entry(ent);
+			base_from_cache = 1;
+			break;
+		}
+
+		if (do_check_packed_object_crc && p->index_version > 1) {
+			struct revindex_entry *revidx = find_pack_revindex(p, obj_offset);
+			off_t len = revidx[1].offset - obj_offset;
+			if (check_pack_crc(p, &w_curs, obj_offset, len, revidx->nr)) {
+				struct object_id oid;
+				nth_packed_object_oid(&oid, p, revidx->nr);
+				error("bad packed object CRC for %s",
+				      oid_to_hex(&oid));
+				mark_bad_packed_object(p, oid.hash);
+				data = NULL;
+				goto out;
+			}
+		}
+
+		type = unpack_object_header(p, &w_curs, &curpos, &size);
+		if (type != OBJ_OFS_DELTA && type != OBJ_REF_DELTA)
+			break;
+
+		base_offset = get_delta_base(p, &w_curs, &curpos, type, obj_offset);
+		if (!base_offset) {
+			error("failed to validate delta base reference "
+			      "at offset %"PRIuMAX" from %s",
+			      (uintmax_t)curpos, p->pack_name);
+			/* bail to phase 2, in hopes of recovery */
+			data = NULL;
+			break;
+		}
+
+		/* push object, proceed to base */
+		if (delta_stack_nr >= delta_stack_alloc
+		    && delta_stack == small_delta_stack) {
+			delta_stack_alloc = alloc_nr(delta_stack_nr);
+			ALLOC_ARRAY(delta_stack, delta_stack_alloc);
+			COPY_ARRAY(delta_stack, small_delta_stack,
+				   delta_stack_nr);
+		} else {
+			ALLOC_GROW(delta_stack, delta_stack_nr+1, delta_stack_alloc);
+		}
+		i = delta_stack_nr++;
+		delta_stack[i].obj_offset = obj_offset;
+		delta_stack[i].curpos = curpos;
+		delta_stack[i].size = size;
+
+		curpos = obj_offset = base_offset;
+	}
+
+	/* PHASE 2: handle the base */
+	switch (type) {
+	case OBJ_OFS_DELTA:
+	case OBJ_REF_DELTA:
+		if (data)
+			BUG("unpack_entry: left loop at a valid delta");
+		break;
+	case OBJ_COMMIT:
+	case OBJ_TREE:
+	case OBJ_BLOB:
+	case OBJ_TAG:
+		if (!base_from_cache)
+			data = unpack_compressed_entry(p, &w_curs, curpos, size);
+		break;
+	default:
+		data = NULL;
+		error("unknown object type %i at offset %"PRIuMAX" in %s",
+		      type, (uintmax_t)obj_offset, p->pack_name);
+	}
+
+	/* PHASE 3: apply deltas in order */
+
+	/* invariants:
+	 *   'data' holds the base data, or NULL if there was corruption
+	 */
+	while (delta_stack_nr) {
+		void *delta_data;
+		void *base = data;
+		void *external_base = NULL;
+		unsigned long delta_size, base_size = size;
+		int i;
+
+		data = NULL;
+
+		if (base)
+			add_delta_base_cache(p, obj_offset, base, base_size, type);
+
+		if (!base) {
+			/*
+			 * We're probably in deep shit, but let's try to fetch
+			 * the required base anyway from another pack or loose.
+			 * This is costly but should happen only in the presence
+			 * of a corrupted pack, and is better than failing outright.
+			 */
+			struct revindex_entry *revidx;
+			struct object_id base_oid;
+			revidx = find_pack_revindex(p, obj_offset);
+			if (revidx) {
+				nth_packed_object_oid(&base_oid, p, revidx->nr);
+				error("failed to read delta base object %s"
+				      " at offset %"PRIuMAX" from %s",
+				      oid_to_hex(&base_oid), (uintmax_t)obj_offset,
+				      p->pack_name);
+				mark_bad_packed_object(p, base_oid.hash);
+				base = read_object(r, &base_oid, &type, &base_size);
+				external_base = base;
+			}
+		}
+
+		i = --delta_stack_nr;
+		obj_offset = delta_stack[i].obj_offset;
+		curpos = delta_stack[i].curpos;
+		delta_size = delta_stack[i].size;
+
+		if (!base)
+			continue;
+
+		delta_data = unpack_compressed_entry(p, &w_curs, curpos, delta_size);
+
+		if (!delta_data) {
+			error("failed to unpack compressed delta "
+			      "at offset %"PRIuMAX" from %s",
+			      (uintmax_t)curpos, p->pack_name);
+			data = NULL;
+			free(external_base);
+			continue;
+		}
+
+		data = patch_delta(base, base_size,
+				   delta_data, delta_size,
+				   &size);
+
+		/*
+		 * We could not apply the delta; warn the user, but keep going.
+		 * Our failure will be noticed either in the next iteration of
+		 * the loop, or if this is the final delta, in the caller when
+		 * we return NULL. Those code paths will take care of making
+		 * a more explicit warning and retrying with another copy of
+		 * the object.
+		 */
+		if (!data)
+			error("failed to apply delta");
+
+		free(delta_data);
+		free(external_base);
+	}
+
+	if (final_type)
+		*final_type = type;
+	if (final_size)
+		*final_size = size;
+
+out:
+	unuse_pack(&w_curs);
+
+	if (delta_stack != small_delta_stack)
+		free(delta_stack);
+
+	return data;
+}
+
+int bsearch_pack(const struct object_id *oid, const struct packed_git *p, uint32_t *result)
+{
+	const unsigned char *index_fanout = p->index_data;
+	const unsigned char *index_lookup;
+	const unsigned int hashsz = the_hash_algo->rawsz;
+	int index_lookup_width;
+
+	if (!index_fanout)
+		BUG("bsearch_pack called without a valid pack-index");
+
+	index_lookup = index_fanout + 4 * 256;
+	if (p->index_version == 1) {
+		index_lookup_width = hashsz + 4;
+		index_lookup += 4;
+	} else {
+		index_lookup_width = hashsz;
+		index_fanout += 8;
+		index_lookup += 8;
+	}
+
+	return bsearch_hash(oid->hash, (const uint32_t*)index_fanout,
+			    index_lookup, index_lookup_width, result);
+}
+
+const unsigned char *nth_packed_object_sha1(struct packed_git *p,
+					    uint32_t n)
+{
+	const unsigned char *index = p->index_data;
+	const unsigned int hashsz = the_hash_algo->rawsz;
+	if (!index) {
+		if (open_pack_index(p))
+			return NULL;
+		index = p->index_data;
+	}
+	if (n >= p->num_objects)
+		return NULL;
+	index += 4 * 256;
+	if (p->index_version == 1) {
+		return index + (hashsz + 4) * n + 4;
+	} else {
+		index += 8;
+		return index + hashsz * n;
+	}
+}
+
+const struct object_id *nth_packed_object_oid(struct object_id *oid,
+					      struct packed_git *p,
+					      uint32_t n)
+{
+	const unsigned char *hash = nth_packed_object_sha1(p, n);
+	if (!hash)
+		return NULL;
+	hashcpy(oid->hash, hash);
+	return oid;
+}
+
+void check_pack_index_ptr(const struct packed_git *p, const void *vptr)
+{
+	const unsigned char *ptr = vptr;
+	const unsigned char *start = p->index_data;
+	const unsigned char *end = start + p->index_size;
+	if (ptr < start)
+		die(_("offset before start of pack index for %s (corrupt index?)"),
+		    p->pack_name);
+	/* No need to check for underflow; .idx files must be at least 8 bytes */
+	if (ptr >= end - 8)
+		die(_("offset beyond end of pack index for %s (truncated index?)"),
+		    p->pack_name);
+}
+
+off_t nth_packed_object_offset(const struct packed_git *p, uint32_t n)
+{
+	const unsigned char *index = p->index_data;
+	const unsigned int hashsz = the_hash_algo->rawsz;
+	index += 4 * 256;
+	if (p->index_version == 1) {
+		return ntohl(*((uint32_t *)(index + (hashsz + 4) * n)));
+	} else {
+		uint32_t off;
+		index += 8 + p->num_objects * (hashsz + 4);
+		off = ntohl(*((uint32_t *)(index + 4 * n)));
+		if (!(off & 0x80000000))
+			return off;
+		index += p->num_objects * 4 + (off & 0x7fffffff) * 8;
+		check_pack_index_ptr(p, index);
+		return get_be64(index);
+	}
+}
+
+off_t find_pack_entry_one(const unsigned char *sha1,
+				  struct packed_git *p)
+{
+	const unsigned char *index = p->index_data;
+	struct object_id oid;
+	uint32_t result;
+
+	if (!index) {
+		if (open_pack_index(p))
+			return 0;
+	}
+
+	hashcpy(oid.hash, sha1);
+	if (bsearch_pack(&oid, p, &result))
+		return nth_packed_object_offset(p, result);
+	return 0;
+}
+
+int is_pack_valid(struct packed_git *p)
+{
+	/* An already open pack is known to be valid. */
+	if (p->pack_fd != -1)
+		return 1;
+
+	/* If the pack has one window completely covering the
+	 * file size, the pack is known to be valid even if
+	 * the descriptor is not currently open.
+	 */
+	if (p->windows) {
+		struct pack_window *w = p->windows;
+
+		if (!w->offset && w->len == p->pack_size)
+			return 1;
+	}
+
+	/* Force the pack to open to prove its valid. */
+	return !open_packed_git(p);
+}
+
+struct packed_git *find_sha1_pack(const unsigned char *sha1,
+				  struct packed_git *packs)
+{
+	struct packed_git *p;
+
+	for (p = packs; p; p = p->next) {
+		if (find_pack_entry_one(sha1, p))
+			return p;
+	}
+	return NULL;
+
+}
+
+static int fill_pack_entry(const struct object_id *oid,
+			   struct pack_entry *e,
+			   struct packed_git *p)
+{
+	off_t offset;
+
+	if (p->num_bad_objects) {
+		unsigned i;
+		for (i = 0; i < p->num_bad_objects; i++)
+			if (hasheq(oid->hash,
+				   p->bad_object_sha1 + the_hash_algo->rawsz * i))
+				return 0;
+	}
+
+	offset = find_pack_entry_one(oid->hash, p);
+	if (!offset)
+		return 0;
+
+	/*
+	 * We are about to tell the caller where they can locate the
+	 * requested object.  We better make sure the packfile is
+	 * still here and can be accessed before supplying that
+	 * answer, as it may have been deleted since the index was
+	 * loaded!
+	 */
+	if (!is_pack_valid(p))
+		return 0;
+	e->offset = offset;
+	e->p = p;
+	return 1;
+}
+
+int find_pack_entry(struct repository *r, const struct object_id *oid, struct pack_entry *e)
+{
+	struct list_head *pos;
+	struct multi_pack_index *m;
+
+	prepare_packed_git(r);
+	if (!r->objects->packed_git && !r->objects->multi_pack_index)
+		return 0;
+
+	for (m = r->objects->multi_pack_index; m; m = m->next) {
+		if (fill_midx_entry(r, oid, e, m))
+			return 1;
+	}
+
+	list_for_each(pos, &r->objects->packed_git_mru) {
+		struct packed_git *p = list_entry(pos, struct packed_git, mru);
+		if (!p->multi_pack_index && fill_pack_entry(oid, e, p)) {
+			list_move(&p->mru, &r->objects->packed_git_mru);
+			return 1;
+		}
+	}
+	return 0;
+}
+
+int has_object_pack(const struct object_id *oid)
+{
+	struct pack_entry e;
+	return find_pack_entry(the_repository, oid, &e);
+}
+
+int has_pack_index(const unsigned char *sha1)
+{
+	struct stat st;
+	if (stat(sha1_pack_index_name(sha1), &st))
+		return 0;
+	return 1;
+}
+
+int for_each_object_in_pack(struct packed_git *p,
+			    each_packed_object_fn cb, void *data,
+			    enum for_each_object_flags flags)
+{
+	uint32_t i;
+	int r = 0;
+
+	if (flags & FOR_EACH_OBJECT_PACK_ORDER) {
+		if (load_pack_revindex(p))
+			return -1;
+	}
+
+	for (i = 0; i < p->num_objects; i++) {
+		uint32_t pos;
+		struct object_id oid;
+
+		if (flags & FOR_EACH_OBJECT_PACK_ORDER)
+			pos = p->revindex[i].nr;
+		else
+			pos = i;
+
+		if (!nth_packed_object_oid(&oid, p, pos))
+			return error("unable to get sha1 of object %u in %s",
+				     pos, p->pack_name);
+
+		r = cb(&oid, p, pos, data);
+		if (r)
+			break;
+	}
+	return r;
+}
+
+int for_each_packed_object(each_packed_object_fn cb, void *data,
+			   enum for_each_object_flags flags)
+{
+	struct packed_git *p;
+	int r = 0;
+	int pack_errors = 0;
+
+	prepare_packed_git(the_repository);
+	for (p = get_all_packs(the_repository); p; p = p->next) {
+		if ((flags & FOR_EACH_OBJECT_LOCAL_ONLY) && !p->pack_local)
+			continue;
+		if ((flags & FOR_EACH_OBJECT_PROMISOR_ONLY) &&
+		    !p->pack_promisor)
+			continue;
+		if (open_pack_index(p)) {
+			pack_errors = 1;
+			continue;
+		}
+		r = for_each_object_in_pack(p, cb, data, flags);
+		if (r)
+			break;
+	}
+	return r ? r : pack_errors;
+}
+
+static int add_promisor_object(const struct object_id *oid,
+			       struct packed_git *pack,
+			       uint32_t pos,
+			       void *set_)
+{
+	struct oidset *set = set_;
+	struct object *obj = parse_object(the_repository, oid);
+	if (!obj)
+		return 1;
+
+	oidset_insert(set, oid);
+
+	/*
+	 * If this is a tree, commit, or tag, the objects it refers
+	 * to are also promisor objects. (Blobs refer to no objects->)
+	 */
+	if (obj->type == OBJ_TREE) {
+		struct tree *tree = (struct tree *)obj;
+		struct tree_desc desc;
+		struct name_entry entry;
+		if (init_tree_desc_gently(&desc, tree->buffer, tree->size))
+			/*
+			 * Error messages are given when packs are
+			 * verified, so do not print any here.
+			 */
+			return 0;
+		while (tree_entry_gently(&desc, &entry))
+			oidset_insert(set, &entry.oid);
+	} else if (obj->type == OBJ_COMMIT) {
+		struct commit *commit = (struct commit *) obj;
+		struct commit_list *parents = commit->parents;
+
+		oidset_insert(set, get_commit_tree_oid(commit));
+		for (; parents; parents = parents->next)
+			oidset_insert(set, &parents->item->object.oid);
+	} else if (obj->type == OBJ_TAG) {
+		struct tag *tag = (struct tag *) obj;
+		oidset_insert(set, &tag->tagged->oid);
+	}
+	return 0;
+}
+
+int is_promisor_object(const struct object_id *oid)
+{
+	static struct oidset promisor_objects;
+	static int promisor_objects_prepared;
+
+	if (!promisor_objects_prepared) {
+		if (repository_format_partial_clone) {
+			for_each_packed_object(add_promisor_object,
+					       &promisor_objects,
+					       FOR_EACH_OBJECT_PROMISOR_ONLY);
+		}
+		promisor_objects_prepared = 1;
+	}
+	return oidset_contains(&promisor_objects, oid);
+}