object-file.c: rename from sha1-file.c

Drop the last remnant of "sha1" in this file and rename it to reflect
that we're not just able to handle SHA-1 these days.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2554 insertions, 0 deletions

diff --git a/object-file.c b/object-file.c
new file mode 100644
index 0000000000..3508598d97
--- /dev/null
+++ b/object-file.c
@@ -0,0 +1,2554 @@
+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) Linus Torvalds, 2005
+ *
+ * This handles basic git object files - packing, unpacking,
+ * creation etc.
+ */
+#include "cache.h"
+#include "config.h"
+#include "string-list.h"
+#include "lockfile.h"
+#include "delta.h"
+#include "pack.h"
+#include "blob.h"
+#include "commit.h"
+#include "run-command.h"
+#include "tag.h"
+#include "tree.h"
+#include "tree-walk.h"
+#include "refs.h"
+#include "pack-revindex.h"
+#include "sha1-lookup.h"
+#include "bulk-checkin.h"
+#include "repository.h"
+#include "replace-object.h"
+#include "streaming.h"
+#include "dir.h"
+#include "list.h"
+#include "mergesort.h"
+#include "quote.h"
+#include "packfile.h"
+#include "object-store.h"
+#include "promisor-remote.h"
+
+/* The maximum size for an object header. */
+#define MAX_HEADER_LEN 32
+
+
+#define EMPTY_TREE_SHA1_BIN_LITERAL \
+	 "\x4b\x82\x5d\xc6\x42\xcb\x6e\xb9\xa0\x60" \
+	 "\xe5\x4b\xf8\xd6\x92\x88\xfb\xee\x49\x04"
+#define EMPTY_TREE_SHA256_BIN_LITERAL \
+	"\x6e\xf1\x9b\x41\x22\x5c\x53\x69\xf1\xc1" \
+	"\x04\xd4\x5d\x8d\x85\xef\xa9\xb0\x57\xb5" \
+	"\x3b\x14\xb4\xb9\xb9\x39\xdd\x74\xde\xcc" \
+	"\x53\x21"
+
+#define EMPTY_BLOB_SHA1_BIN_LITERAL \
+	"\xe6\x9d\xe2\x9b\xb2\xd1\xd6\x43\x4b\x8b" \
+	"\x29\xae\x77\x5a\xd8\xc2\xe4\x8c\x53\x91"
+#define EMPTY_BLOB_SHA256_BIN_LITERAL \
+	"\x47\x3a\x0f\x4c\x3b\xe8\xa9\x36\x81\xa2" \
+	"\x67\xe3\xb1\xe9\xa7\xdc\xda\x11\x85\x43" \
+	"\x6f\xe1\x41\xf7\x74\x91\x20\xa3\x03\x72" \
+	"\x18\x13"
+
+const struct object_id null_oid;
+static const struct object_id empty_tree_oid = {
+	EMPTY_TREE_SHA1_BIN_LITERAL
+};
+static const struct object_id empty_blob_oid = {
+	EMPTY_BLOB_SHA1_BIN_LITERAL
+};
+static const struct object_id empty_tree_oid_sha256 = {
+	EMPTY_TREE_SHA256_BIN_LITERAL
+};
+static const struct object_id empty_blob_oid_sha256 = {
+	EMPTY_BLOB_SHA256_BIN_LITERAL
+};
+
+static void git_hash_sha1_init(git_hash_ctx *ctx)
+{
+	git_SHA1_Init(&ctx->sha1);
+}
+
+static void git_hash_sha1_clone(git_hash_ctx *dst, const git_hash_ctx *src)
+{
+	git_SHA1_Clone(&dst->sha1, &src->sha1);
+}
+
+static void git_hash_sha1_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	git_SHA1_Update(&ctx->sha1, data, len);
+}
+
+static void git_hash_sha1_final(unsigned char *hash, git_hash_ctx *ctx)
+{
+	git_SHA1_Final(hash, &ctx->sha1);
+}
+
+
+static void git_hash_sha256_init(git_hash_ctx *ctx)
+{
+	git_SHA256_Init(&ctx->sha256);
+}
+
+static void git_hash_sha256_clone(git_hash_ctx *dst, const git_hash_ctx *src)
+{
+	git_SHA256_Clone(&dst->sha256, &src->sha256);
+}
+
+static void git_hash_sha256_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	git_SHA256_Update(&ctx->sha256, data, len);
+}
+
+static void git_hash_sha256_final(unsigned char *hash, git_hash_ctx *ctx)
+{
+	git_SHA256_Final(hash, &ctx->sha256);
+}
+
+static void git_hash_unknown_init(git_hash_ctx *ctx)
+{
+	BUG("trying to init unknown hash");
+}
+
+static void git_hash_unknown_clone(git_hash_ctx *dst, const git_hash_ctx *src)
+{
+	BUG("trying to clone unknown hash");
+}
+
+static void git_hash_unknown_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	BUG("trying to update unknown hash");
+}
+
+static void git_hash_unknown_final(unsigned char *hash, git_hash_ctx *ctx)
+{
+	BUG("trying to finalize unknown hash");
+}
+
+const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
+	{
+		NULL,
+		0x00000000,
+		0,
+		0,
+		0,
+		git_hash_unknown_init,
+		git_hash_unknown_clone,
+		git_hash_unknown_update,
+		git_hash_unknown_final,
+		NULL,
+		NULL,
+	},
+	{
+		"sha1",
+		/* "sha1", big-endian */
+		0x73686131,
+		GIT_SHA1_RAWSZ,
+		GIT_SHA1_HEXSZ,
+		GIT_SHA1_BLKSZ,
+		git_hash_sha1_init,
+		git_hash_sha1_clone,
+		git_hash_sha1_update,
+		git_hash_sha1_final,
+		&empty_tree_oid,
+		&empty_blob_oid,
+	},
+	{
+		"sha256",
+		/* "s256", big-endian */
+		0x73323536,
+		GIT_SHA256_RAWSZ,
+		GIT_SHA256_HEXSZ,
+		GIT_SHA256_BLKSZ,
+		git_hash_sha256_init,
+		git_hash_sha256_clone,
+		git_hash_sha256_update,
+		git_hash_sha256_final,
+		&empty_tree_oid_sha256,
+		&empty_blob_oid_sha256,
+	}
+};
+
+const char *empty_tree_oid_hex(void)
+{
+	static char buf[GIT_MAX_HEXSZ + 1];
+	return oid_to_hex_r(buf, the_hash_algo->empty_tree);
+}
+
+const char *empty_blob_oid_hex(void)
+{
+	static char buf[GIT_MAX_HEXSZ + 1];
+	return oid_to_hex_r(buf, the_hash_algo->empty_blob);
+}
+
+int hash_algo_by_name(const char *name)
+{
+	int i;
+	if (!name)
+		return GIT_HASH_UNKNOWN;
+	for (i = 1; i < GIT_HASH_NALGOS; i++)
+		if (!strcmp(name, hash_algos[i].name))
+			return i;
+	return GIT_HASH_UNKNOWN;
+}
+
+int hash_algo_by_id(uint32_t format_id)
+{
+	int i;
+	for (i = 1; i < GIT_HASH_NALGOS; i++)
+		if (format_id == hash_algos[i].format_id)
+			return i;
+	return GIT_HASH_UNKNOWN;
+}
+
+int hash_algo_by_length(int len)
+{
+	int i;
+	for (i = 1; i < GIT_HASH_NALGOS; i++)
+		if (len == hash_algos[i].rawsz)
+			return i;
+	return GIT_HASH_UNKNOWN;
+}
+
+/*
+ * This is meant to hold a *small* number of objects that you would
+ * want read_object_file() to be able to return, but yet you do not want
+ * to write them into the object store (e.g. a browse-only
+ * application).
+ */
+static struct cached_object {
+	struct object_id oid;
+	enum object_type type;
+	void *buf;
+	unsigned long size;
+} *cached_objects;
+static int cached_object_nr, cached_object_alloc;
+
+static struct cached_object empty_tree = {
+	{ EMPTY_TREE_SHA1_BIN_LITERAL },
+	OBJ_TREE,
+	"",
+	0
+};
+
+static struct cached_object *find_cached_object(const struct object_id *oid)
+{
+	int i;
+	struct cached_object *co = cached_objects;
+
+	for (i = 0; i < cached_object_nr; i++, co++) {
+		if (oideq(&co->oid, oid))
+			return co;
+	}
+	if (oideq(oid, the_hash_algo->empty_tree))
+		return &empty_tree;
+	return NULL;
+}
+
+
+static int get_conv_flags(unsigned flags)
+{
+	if (flags & HASH_RENORMALIZE)
+		return CONV_EOL_RENORMALIZE;
+	else if (flags & HASH_WRITE_OBJECT)
+		return global_conv_flags_eol | CONV_WRITE_OBJECT;
+	else
+		return 0;
+}
+
+
+int mkdir_in_gitdir(const char *path)
+{
+	if (mkdir(path, 0777)) {
+		int saved_errno = errno;
+		struct stat st;
+		struct strbuf sb = STRBUF_INIT;
+
+		if (errno != EEXIST)
+			return -1;
+		/*
+		 * Are we looking at a path in a symlinked worktree
+		 * whose original repository does not yet have it?
+		 * e.g. .git/rr-cache pointing at its original
+		 * repository in which the user hasn't performed any
+		 * conflict resolution yet?
+		 */
+		if (lstat(path, &st) || !S_ISLNK(st.st_mode) ||
+		    strbuf_readlink(&sb, path, st.st_size) ||
+		    !is_absolute_path(sb.buf) ||
+		    mkdir(sb.buf, 0777)) {
+			strbuf_release(&sb);
+			errno = saved_errno;
+			return -1;
+		}
+		strbuf_release(&sb);
+	}
+	return adjust_shared_perm(path);
+}
+
+static enum scld_error safe_create_leading_directories_1(char *path, int share)
+{
+	char *next_component = path + offset_1st_component(path);
+	enum scld_error ret = SCLD_OK;
+
+	while (ret == SCLD_OK && next_component) {
+		struct stat st;
+		char *slash = next_component, slash_character;
+
+		while (*slash && !is_dir_sep(*slash))
+			slash++;
+
+		if (!*slash)
+			break;
+
+		next_component = slash + 1;
+		while (is_dir_sep(*next_component))
+			next_component++;
+		if (!*next_component)
+			break;
+
+		slash_character = *slash;
+		*slash = '\0';
+		if (!stat(path, &st)) {
+			/* path exists */
+			if (!S_ISDIR(st.st_mode)) {
+				errno = ENOTDIR;
+				ret = SCLD_EXISTS;
+			}
+		} else if (mkdir(path, 0777)) {
+			if (errno == EEXIST &&
+			    !stat(path, &st) && S_ISDIR(st.st_mode))
+				; /* somebody created it since we checked */
+			else if (errno == ENOENT)
+				/*
+				 * Either mkdir() failed because
+				 * somebody just pruned the containing
+				 * directory, or stat() failed because
+				 * the file that was in our way was
+				 * just removed.  Either way, inform
+				 * the caller that it might be worth
+				 * trying again:
+				 */
+				ret = SCLD_VANISHED;
+			else
+				ret = SCLD_FAILED;
+		} else if (share && adjust_shared_perm(path)) {
+			ret = SCLD_PERMS;
+		}
+		*slash = slash_character;
+	}
+	return ret;
+}
+
+enum scld_error safe_create_leading_directories(char *path)
+{
+	return safe_create_leading_directories_1(path, 1);
+}
+
+enum scld_error safe_create_leading_directories_no_share(char *path)
+{
+	return safe_create_leading_directories_1(path, 0);
+}
+
+enum scld_error safe_create_leading_directories_const(const char *path)
+{
+	int save_errno;
+	/* path points to cache entries, so xstrdup before messing with it */
+	char *buf = xstrdup(path);
+	enum scld_error result = safe_create_leading_directories(buf);
+
+	save_errno = errno;
+	free(buf);
+	errno = save_errno;
+	return result;
+}
+
+int raceproof_create_file(const char *path, create_file_fn fn, void *cb)
+{
+	/*
+	 * The number of times we will try to remove empty directories
+	 * in the way of path. This is only 1 because if another
+	 * process is racily creating directories that conflict with
+	 * us, we don't want to fight against them.
+	 */
+	int remove_directories_remaining = 1;
+
+	/*
+	 * The number of times that we will try to create the
+	 * directories containing path. We are willing to attempt this
+	 * more than once, because another process could be trying to
+	 * clean up empty directories at the same time as we are
+	 * trying to create them.
+	 */
+	int create_directories_remaining = 3;
+
+	/* A scratch copy of path, filled lazily if we need it: */
+	struct strbuf path_copy = STRBUF_INIT;
+
+	int ret, save_errno;
+
+	/* Sanity check: */
+	assert(*path);
+
+retry_fn:
+	ret = fn(path, cb);
+	save_errno = errno;
+	if (!ret)
+		goto out;
+
+	if (errno == EISDIR && remove_directories_remaining-- > 0) {
+		/*
+		 * A directory is in the way. Maybe it is empty; try
+		 * to remove it:
+		 */
+		if (!path_copy.len)
+			strbuf_addstr(&path_copy, path);
+
+		if (!remove_dir_recursively(&path_copy, REMOVE_DIR_EMPTY_ONLY))
+			goto retry_fn;
+	} else if (errno == ENOENT && create_directories_remaining-- > 0) {
+		/*
+		 * Maybe the containing directory didn't exist, or
+		 * maybe it was just deleted by a process that is
+		 * racing with us to clean up empty directories. Try
+		 * to create it:
+		 */
+		enum scld_error scld_result;
+
+		if (!path_copy.len)
+			strbuf_addstr(&path_copy, path);
+
+		do {
+			scld_result = safe_create_leading_directories(path_copy.buf);
+			if (scld_result == SCLD_OK)
+				goto retry_fn;
+		} while (scld_result == SCLD_VANISHED && create_directories_remaining-- > 0);
+	}
+
+out:
+	strbuf_release(&path_copy);
+	errno = save_errno;
+	return ret;
+}
+
+static void fill_loose_path(struct strbuf *buf, const struct object_id *oid)
+{
+	int i;
+	for (i = 0; i < the_hash_algo->rawsz; i++) {
+		static char hex[] = "0123456789abcdef";
+		unsigned int val = oid->hash[i];
+		strbuf_addch(buf, hex[val >> 4]);
+		strbuf_addch(buf, hex[val & 0xf]);
+		if (!i)
+			strbuf_addch(buf, '/');
+	}
+}
+
+static const char *odb_loose_path(struct object_directory *odb,
+				  struct strbuf *buf,
+				  const struct object_id *oid)
+{
+	strbuf_reset(buf);
+	strbuf_addstr(buf, odb->path);
+	strbuf_addch(buf, '/');
+	fill_loose_path(buf, oid);
+	return buf->buf;
+}
+
+const char *loose_object_path(struct repository *r, struct strbuf *buf,
+			      const struct object_id *oid)
+{
+	return odb_loose_path(r->objects->odb, buf, oid);
+}
+
+/*
+ * Return non-zero iff the path is usable as an alternate object database.
+ */
+static int alt_odb_usable(struct raw_object_store *o,
+			  struct strbuf *path,
+			  const char *normalized_objdir)
+{
+	struct object_directory *odb;
+
+	/* Detect cases where alternate disappeared */
+	if (!is_directory(path->buf)) {
+		error(_("object directory %s does not exist; "
+			"check .git/objects/info/alternates"),
+		      path->buf);
+		return 0;
+	}
+
+	/*
+	 * Prevent the common mistake of listing the same
+	 * thing twice, or object directory itself.
+	 */
+	for (odb = o->odb; odb; odb = odb->next) {
+		if (!fspathcmp(path->buf, odb->path))
+			return 0;
+	}
+	if (!fspathcmp(path->buf, normalized_objdir))
+		return 0;
+
+	return 1;
+}
+
+/*
+ * Prepare alternate object database registry.
+ *
+ * The variable alt_odb_list points at the list of struct
+ * object_directory.  The elements on this list come from
+ * non-empty elements from colon separated ALTERNATE_DB_ENVIRONMENT
+ * environment variable, and $GIT_OBJECT_DIRECTORY/info/alternates,
+ * whose contents is similar to that environment variable but can be
+ * LF separated.  Its base points at a statically allocated buffer that
+ * contains "/the/directory/corresponding/to/.git/objects/...", while
+ * its name points just after the slash at the end of ".git/objects/"
+ * in the example above, and has enough space to hold all hex characters
+ * of the object ID, an extra slash for the first level indirection, and
+ * the terminating NUL.
+ */
+static void read_info_alternates(struct repository *r,
+				 const char *relative_base,
+				 int depth);
+static int link_alt_odb_entry(struct repository *r, const char *entry,
+	const char *relative_base, int depth, const char *normalized_objdir)
+{
+	struct object_directory *ent;
+	struct strbuf pathbuf = STRBUF_INIT;
+
+	if (!is_absolute_path(entry) && relative_base) {
+		strbuf_realpath(&pathbuf, relative_base, 1);
+		strbuf_addch(&pathbuf, '/');
+	}
+	strbuf_addstr(&pathbuf, entry);
+
+	if (strbuf_normalize_path(&pathbuf) < 0 && relative_base) {
+		error(_("unable to normalize alternate object path: %s"),
+		      pathbuf.buf);
+		strbuf_release(&pathbuf);
+		return -1;
+	}
+
+	/*
+	 * The trailing slash after the directory name is given by
+	 * this function at the end. Remove duplicates.
+	 */
+	while (pathbuf.len && pathbuf.buf[pathbuf.len - 1] == '/')
+		strbuf_setlen(&pathbuf, pathbuf.len - 1);
+
+	if (!alt_odb_usable(r->objects, &pathbuf, normalized_objdir)) {
+		strbuf_release(&pathbuf);
+		return -1;
+	}
+
+	ent = xcalloc(1, sizeof(*ent));
+	ent->path = xstrdup(pathbuf.buf);
+
+	/* add the alternate entry */
+	*r->objects->odb_tail = ent;
+	r->objects->odb_tail = &(ent->next);
+	ent->next = NULL;
+
+	/* recursively add alternates */
+	read_info_alternates(r, pathbuf.buf, depth + 1);
+
+	strbuf_release(&pathbuf);
+	return 0;
+}
+
+static const char *parse_alt_odb_entry(const char *string,
+				       int sep,
+				       struct strbuf *out)
+{
+	const char *end;
+
+	strbuf_reset(out);
+
+	if (*string == '#') {
+		/* comment; consume up to next separator */
+		end = strchrnul(string, sep);
+	} else if (*string == '"' && !unquote_c_style(out, string, &end)) {
+		/*
+		 * quoted path; unquote_c_style has copied the
+		 * data for us and set "end". Broken quoting (e.g.,
+		 * an entry that doesn't end with a quote) falls
+		 * back to the unquoted case below.
+		 */
+	} else {
+		/* normal, unquoted path */
+		end = strchrnul(string, sep);
+		strbuf_add(out, string, end - string);
+	}
+
+	if (*end)
+		end++;
+	return end;
+}
+
+static void link_alt_odb_entries(struct repository *r, const char *alt,
+				 int sep, const char *relative_base, int depth)
+{
+	struct strbuf objdirbuf = STRBUF_INIT;
+	struct strbuf entry = STRBUF_INIT;
+
+	if (!alt || !*alt)
+		return;
+
+	if (depth > 5) {
+		error(_("%s: ignoring alternate object stores, nesting too deep"),
+				relative_base);
+		return;
+	}
+
+	strbuf_add_absolute_path(&objdirbuf, r->objects->odb->path);
+	if (strbuf_normalize_path(&objdirbuf) < 0)
+		die(_("unable to normalize object directory: %s"),
+		    objdirbuf.buf);
+
+	while (*alt) {
+		alt = parse_alt_odb_entry(alt, sep, &entry);
+		if (!entry.len)
+			continue;
+		link_alt_odb_entry(r, entry.buf,
+				   relative_base, depth, objdirbuf.buf);
+	}
+	strbuf_release(&entry);
+	strbuf_release(&objdirbuf);
+}
+
+static void read_info_alternates(struct repository *r,
+				 const char *relative_base,
+				 int depth)
+{
+	char *path;
+	struct strbuf buf = STRBUF_INIT;
+
+	path = xstrfmt("%s/info/alternates", relative_base);
+	if (strbuf_read_file(&buf, path, 1024) < 0) {
+		warn_on_fopen_errors(path);
+		free(path);
+		return;
+	}
+
+	link_alt_odb_entries(r, buf.buf, '\n', relative_base, depth);
+	strbuf_release(&buf);
+	free(path);
+}
+
+void add_to_alternates_file(const char *reference)
+{
+	struct lock_file lock = LOCK_INIT;
+	char *alts = git_pathdup("objects/info/alternates");
+	FILE *in, *out;
+	int found = 0;
+
+	hold_lock_file_for_update(&lock, alts, LOCK_DIE_ON_ERROR);
+	out = fdopen_lock_file(&lock, "w");
+	if (!out)
+		die_errno(_("unable to fdopen alternates lockfile"));
+
+	in = fopen(alts, "r");
+	if (in) {
+		struct strbuf line = STRBUF_INIT;
+
+		while (strbuf_getline(&line, in) != EOF) {
+			if (!strcmp(reference, line.buf)) {
+				found = 1;
+				break;
+			}
+			fprintf_or_die(out, "%s\n", line.buf);
+		}
+
+		strbuf_release(&line);
+		fclose(in);
+	}
+	else if (errno != ENOENT)
+		die_errno(_("unable to read alternates file"));
+
+	if (found) {
+		rollback_lock_file(&lock);
+	} else {
+		fprintf_or_die(out, "%s\n", reference);
+		if (commit_lock_file(&lock))
+			die_errno(_("unable to move new alternates file into place"));
+		if (the_repository->objects->loaded_alternates)
+			link_alt_odb_entries(the_repository, reference,
+					     '\n', NULL, 0);
+	}
+	free(alts);
+}
+
+void add_to_alternates_memory(const char *reference)
+{
+	/*
+	 * Make sure alternates are initialized, or else our entry may be
+	 * overwritten when they are.
+	 */
+	prepare_alt_odb(the_repository);
+
+	link_alt_odb_entries(the_repository, reference,
+			     '\n', NULL, 0);
+}
+
+/*
+ * Compute the exact path an alternate is at and returns it. In case of
+ * error NULL is returned and the human readable error is added to `err`
+ * `path` may be relative and should point to $GIT_DIR.
+ * `err` must not be null.
+ */
+char *compute_alternate_path(const char *path, struct strbuf *err)
+{
+	char *ref_git = NULL;
+	const char *repo;
+	int seen_error = 0;
+
+	ref_git = real_pathdup(path, 0);
+	if (!ref_git) {
+		seen_error = 1;
+		strbuf_addf(err, _("path '%s' does not exist"), path);
+		goto out;
+	}
+
+	repo = read_gitfile(ref_git);
+	if (!repo)
+		repo = read_gitfile(mkpath("%s/.git", ref_git));
+	if (repo) {
+		free(ref_git);
+		ref_git = xstrdup(repo);
+	}
+
+	if (!repo && is_directory(mkpath("%s/.git/objects", ref_git))) {
+		char *ref_git_git = mkpathdup("%s/.git", ref_git);
+		free(ref_git);
+		ref_git = ref_git_git;
+	} else if (!is_directory(mkpath("%s/objects", ref_git))) {
+		struct strbuf sb = STRBUF_INIT;
+		seen_error = 1;
+		if (get_common_dir(&sb, ref_git)) {
+			strbuf_addf(err,
+				    _("reference repository '%s' as a linked "
+				      "checkout is not supported yet."),
+				    path);
+			goto out;
+		}
+
+		strbuf_addf(err, _("reference repository '%s' is not a "
+					"local repository."), path);
+		goto out;
+	}
+
+	if (!access(mkpath("%s/shallow", ref_git), F_OK)) {
+		strbuf_addf(err, _("reference repository '%s' is shallow"),
+			    path);
+		seen_error = 1;
+		goto out;
+	}
+
+	if (!access(mkpath("%s/info/grafts", ref_git), F_OK)) {
+		strbuf_addf(err,
+			    _("reference repository '%s' is grafted"),
+			    path);
+		seen_error = 1;
+		goto out;
+	}
+
+out:
+	if (seen_error) {
+		FREE_AND_NULL(ref_git);
+	}
+
+	return ref_git;
+}
+
+static void fill_alternate_refs_command(struct child_process *cmd,
+					const char *repo_path)
+{
+	const char *value;
+
+	if (!git_config_get_value("core.alternateRefsCommand", &value)) {
+		cmd->use_shell = 1;
+
+		strvec_push(&cmd->args, value);
+		strvec_push(&cmd->args, repo_path);
+	} else {
+		cmd->git_cmd = 1;
+
+		strvec_pushf(&cmd->args, "--git-dir=%s", repo_path);
+		strvec_push(&cmd->args, "for-each-ref");
+		strvec_push(&cmd->args, "--format=%(objectname)");
+
+		if (!git_config_get_value("core.alternateRefsPrefixes", &value)) {
+			strvec_push(&cmd->args, "--");
+			strvec_split(&cmd->args, value);
+		}
+	}
+
+	cmd->env = local_repo_env;
+	cmd->out = -1;
+}
+
+static void read_alternate_refs(const char *path,
+				alternate_ref_fn *cb,
+				void *data)
+{
+	struct child_process cmd = CHILD_PROCESS_INIT;
+	struct strbuf line = STRBUF_INIT;
+	FILE *fh;
+
+	fill_alternate_refs_command(&cmd, path);
+
+	if (start_command(&cmd))
+		return;
+
+	fh = xfdopen(cmd.out, "r");
+	while (strbuf_getline_lf(&line, fh) != EOF) {
+		struct object_id oid;
+		const char *p;
+
+		if (parse_oid_hex(line.buf, &oid, &p) || *p) {
+			warning(_("invalid line while parsing alternate refs: %s"),
+				line.buf);
+			break;
+		}
+
+		cb(&oid, data);
+	}
+
+	fclose(fh);
+	finish_command(&cmd);
+	strbuf_release(&line);
+}
+
+struct alternate_refs_data {
+	alternate_ref_fn *fn;
+	void *data;
+};
+
+static int refs_from_alternate_cb(struct object_directory *e,
+				  void *data)
+{
+	struct strbuf path = STRBUF_INIT;
+	size_t base_len;
+	struct alternate_refs_data *cb = data;
+
+	if (!strbuf_realpath(&path, e->path, 0))
+		goto out;
+	if (!strbuf_strip_suffix(&path, "/objects"))
+		goto out;
+	base_len = path.len;
+
+	/* Is this a git repository with refs? */
+	strbuf_addstr(&path, "/refs");
+	if (!is_directory(path.buf))
+		goto out;
+	strbuf_setlen(&path, base_len);
+
+	read_alternate_refs(path.buf, cb->fn, cb->data);
+
+out:
+	strbuf_release(&path);
+	return 0;
+}
+
+void for_each_alternate_ref(alternate_ref_fn fn, void *data)
+{
+	struct alternate_refs_data cb;
+	cb.fn = fn;
+	cb.data = data;
+	foreach_alt_odb(refs_from_alternate_cb, &cb);
+}
+
+int foreach_alt_odb(alt_odb_fn fn, void *cb)
+{
+	struct object_directory *ent;
+	int r = 0;
+
+	prepare_alt_odb(the_repository);
+	for (ent = the_repository->objects->odb->next; ent; ent = ent->next) {
+		r = fn(ent, cb);
+		if (r)
+			break;
+	}
+	return r;
+}
+
+void prepare_alt_odb(struct repository *r)
+{
+	if (r->objects->loaded_alternates)
+		return;
+
+	link_alt_odb_entries(r, r->objects->alternate_db, PATH_SEP, NULL, 0);
+
+	read_info_alternates(r, r->objects->odb->path, 0);
+	r->objects->loaded_alternates = 1;
+}
+
+/* Returns 1 if we have successfully freshened the file, 0 otherwise. */
+static int freshen_file(const char *fn)
+{
+	return !utime(fn, NULL);
+}
+
+/*
+ * All of the check_and_freshen functions return 1 if the file exists and was
+ * freshened (if freshening was requested), 0 otherwise. If they return
+ * 0, you should not assume that it is safe to skip a write of the object (it
+ * either does not exist on disk, or has a stale mtime and may be subject to
+ * pruning).
+ */
+int check_and_freshen_file(const char *fn, int freshen)
+{
+	if (access(fn, F_OK))
+		return 0;
+	if (freshen && !freshen_file(fn))
+		return 0;
+	return 1;
+}
+
+static int check_and_freshen_odb(struct object_directory *odb,
+				 const struct object_id *oid,
+				 int freshen)
+{
+	static struct strbuf path = STRBUF_INIT;
+	odb_loose_path(odb, &path, oid);
+	return check_and_freshen_file(path.buf, freshen);
+}
+
+static int check_and_freshen_local(const struct object_id *oid, int freshen)
+{
+	return check_and_freshen_odb(the_repository->objects->odb, oid, freshen);
+}
+
+static int check_and_freshen_nonlocal(const struct object_id *oid, int freshen)
+{
+	struct object_directory *odb;
+
+	prepare_alt_odb(the_repository);
+	for (odb = the_repository->objects->odb->next; odb; odb = odb->next) {
+		if (check_and_freshen_odb(odb, oid, freshen))
+			return 1;
+	}
+	return 0;
+}
+
+static int check_and_freshen(const struct object_id *oid, int freshen)
+{
+	return check_and_freshen_local(oid, freshen) ||
+	       check_and_freshen_nonlocal(oid, freshen);
+}
+
+int has_loose_object_nonlocal(const struct object_id *oid)
+{
+	return check_and_freshen_nonlocal(oid, 0);
+}
+
+static int has_loose_object(const struct object_id *oid)
+{
+	return check_and_freshen(oid, 0);
+}
+
+static void mmap_limit_check(size_t length)
+{
+	static size_t limit = 0;
+	if (!limit) {
+		limit = git_env_ulong("GIT_MMAP_LIMIT", 0);
+		if (!limit)
+			limit = SIZE_MAX;
+	}
+	if (length > limit)
+		die(_("attempting to mmap %"PRIuMAX" over limit %"PRIuMAX),
+		    (uintmax_t)length, (uintmax_t)limit);
+}
+
+void *xmmap_gently(void *start, size_t length,
+		  int prot, int flags, int fd, off_t offset)
+{
+	void *ret;
+
+	mmap_limit_check(length);
+	ret = mmap(start, length, prot, flags, fd, offset);
+	if (ret == MAP_FAILED && !length)
+		ret = NULL;
+	return ret;
+}
+
+void *xmmap(void *start, size_t length,
+	int prot, int flags, int fd, off_t offset)
+{
+	void *ret = xmmap_gently(start, length, prot, flags, fd, offset);
+	if (ret == MAP_FAILED)
+		die_errno(_("mmap failed"));
+	return ret;
+}
+
+/*
+ * With an in-core object data in "map", rehash it to make sure the
+ * object name actually matches "oid" to detect object corruption.
+ * With "map" == NULL, try reading the object named with "oid" using
+ * the streaming interface and rehash it to do the same.
+ */
+int check_object_signature(struct repository *r, const struct object_id *oid,
+			   void *map, unsigned long size, const char *type)
+{
+	struct object_id real_oid;
+	enum object_type obj_type;
+	struct git_istream *st;
+	git_hash_ctx c;
+	char hdr[MAX_HEADER_LEN];
+	int hdrlen;
+
+	if (map) {
+		hash_object_file(r->hash_algo, map, size, type, &real_oid);
+		return !oideq(oid, &real_oid) ? -1 : 0;
+	}
+
+	st = open_istream(r, oid, &obj_type, &size, NULL);
+	if (!st)
+		return -1;
+
+	/* Generate the header */
+	hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %"PRIuMAX , type_name(obj_type), (uintmax_t)size) + 1;
+
+	/* Sha1.. */
+	r->hash_algo->init_fn(&c);
+	r->hash_algo->update_fn(&c, hdr, hdrlen);
+	for (;;) {
+		char buf[1024 * 16];
+		ssize_t readlen = read_istream(st, buf, sizeof(buf));
+
+		if (readlen < 0) {
+			close_istream(st);
+			return -1;
+		}
+		if (!readlen)
+			break;
+		r->hash_algo->update_fn(&c, buf, readlen);
+	}
+	r->hash_algo->final_fn(real_oid.hash, &c);
+	close_istream(st);
+	return !oideq(oid, &real_oid) ? -1 : 0;
+}
+
+int git_open_cloexec(const char *name, int flags)
+{
+	int fd;
+	static int o_cloexec = O_CLOEXEC;
+
+	fd = open(name, flags | o_cloexec);
+	if ((o_cloexec & O_CLOEXEC) && fd < 0 && errno == EINVAL) {
+		/* Try again w/o O_CLOEXEC: the kernel might not support it */
+		o_cloexec &= ~O_CLOEXEC;
+		fd = open(name, flags | o_cloexec);
+	}
+
+#if defined(F_GETFD) && defined(F_SETFD) && defined(FD_CLOEXEC)
+	{
+		static int fd_cloexec = FD_CLOEXEC;
+
+		if (!o_cloexec && 0 <= fd && fd_cloexec) {
+			/* Opened w/o O_CLOEXEC?  try with fcntl(2) to add it */
+			int flags = fcntl(fd, F_GETFD);
+			if (fcntl(fd, F_SETFD, flags | fd_cloexec))
+				fd_cloexec = 0;
+		}
+	}
+#endif
+	return fd;
+}
+
+/*
+ * Find "oid" as a loose object in the local repository or in an alternate.
+ * Returns 0 on success, negative on failure.
+ *
+ * The "path" out-parameter will give the path of the object we found (if any).
+ * Note that it may point to static storage and is only valid until another
+ * call to stat_loose_object().
+ */
+static int stat_loose_object(struct repository *r, const struct object_id *oid,
+			     struct stat *st, const char **path)
+{
+	struct object_directory *odb;
+	static struct strbuf buf = STRBUF_INIT;
+
+	prepare_alt_odb(r);
+	for (odb = r->objects->odb; odb; odb = odb->next) {
+		*path = odb_loose_path(odb, &buf, oid);
+		if (!lstat(*path, st))
+			return 0;
+	}
+
+	return -1;
+}
+
+/*
+ * Like stat_loose_object(), but actually open the object and return the
+ * descriptor. See the caveats on the "path" parameter above.
+ */
+static int open_loose_object(struct repository *r,
+			     const struct object_id *oid, const char **path)
+{
+	int fd;
+	struct object_directory *odb;
+	int most_interesting_errno = ENOENT;
+	static struct strbuf buf = STRBUF_INIT;
+
+	prepare_alt_odb(r);
+	for (odb = r->objects->odb; odb; odb = odb->next) {
+		*path = odb_loose_path(odb, &buf, oid);
+		fd = git_open(*path);
+		if (fd >= 0)
+			return fd;
+
+		if (most_interesting_errno == ENOENT)
+			most_interesting_errno = errno;
+	}
+	errno = most_interesting_errno;
+	return -1;
+}
+
+static int quick_has_loose(struct repository *r,
+			   const struct object_id *oid)
+{
+	struct object_directory *odb;
+
+	prepare_alt_odb(r);
+	for (odb = r->objects->odb; odb; odb = odb->next) {
+		if (oid_array_lookup(odb_loose_cache(odb, oid), oid) >= 0)
+			return 1;
+	}
+	return 0;
+}
+
+/*
+ * Map the loose object at "path" if it is not NULL, or the path found by
+ * searching for a loose object named "oid".
+ */
+static void *map_loose_object_1(struct repository *r, const char *path,
+			     const struct object_id *oid, unsigned long *size)
+{
+	void *map;
+	int fd;
+
+	if (path)
+		fd = git_open(path);
+	else
+		fd = open_loose_object(r, oid, &path);
+	map = NULL;
+	if (fd >= 0) {
+		struct stat st;
+
+		if (!fstat(fd, &st)) {
+			*size = xsize_t(st.st_size);
+			if (!*size) {
+				/* mmap() is forbidden on empty files */
+				error(_("object file %s is empty"), path);
+				close(fd);
+				return NULL;
+			}
+			map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
+		}
+		close(fd);
+	}
+	return map;
+}
+
+void *map_loose_object(struct repository *r,
+		       const struct object_id *oid,
+		       unsigned long *size)
+{
+	return map_loose_object_1(r, NULL, oid, size);
+}
+
+static int unpack_loose_short_header(git_zstream *stream,
+				     unsigned char *map, unsigned long mapsize,
+				     void *buffer, unsigned long bufsiz)
+{
+	int ret;
+
+	/* Get the data stream */
+	memset(stream, 0, sizeof(*stream));
+	stream->next_in = map;
+	stream->avail_in = mapsize;
+	stream->next_out = buffer;
+	stream->avail_out = bufsiz;
+
+	git_inflate_init(stream);
+	obj_read_unlock();
+	ret = git_inflate(stream, 0);
+	obj_read_lock();
+
+	return ret;
+}
+
+int unpack_loose_header(git_zstream *stream,
+			unsigned char *map, unsigned long mapsize,
+			void *buffer, unsigned long bufsiz)
+{
+	int status = unpack_loose_short_header(stream, map, mapsize,
+					       buffer, bufsiz);
+
+	if (status < Z_OK)
+		return status;
+
+	/* Make sure we have the terminating NUL */
+	if (!memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
+		return -1;
+	return 0;
+}
+
+static int unpack_loose_header_to_strbuf(git_zstream *stream, unsigned char *map,
+					 unsigned long mapsize, void *buffer,
+					 unsigned long bufsiz, struct strbuf *header)
+{
+	int status;
+
+	status = unpack_loose_short_header(stream, map, mapsize, buffer, bufsiz);
+	if (status < Z_OK)
+		return -1;
+
+	/*
+	 * Check if entire header is unpacked in the first iteration.
+	 */
+	if (memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
+		return 0;
+
+	/*
+	 * buffer[0..bufsiz] was not large enough.  Copy the partial
+	 * result out to header, and then append the result of further
+	 * reading the stream.
+	 */
+	strbuf_add(header, buffer, stream->next_out - (unsigned char *)buffer);
+	stream->next_out = buffer;
+	stream->avail_out = bufsiz;
+
+	do {
+		obj_read_unlock();
+		status = git_inflate(stream, 0);
+		obj_read_lock();
+		strbuf_add(header, buffer, stream->next_out - (unsigned char *)buffer);
+		if (memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
+			return 0;
+		stream->next_out = buffer;
+		stream->avail_out = bufsiz;
+	} while (status != Z_STREAM_END);
+	return -1;
+}
+
+static void *unpack_loose_rest(git_zstream *stream,
+			       void *buffer, unsigned long size,
+			       const struct object_id *oid)
+{
+	int bytes = strlen(buffer) + 1;
+	unsigned char *buf = xmallocz(size);
+	unsigned long n;
+	int status = Z_OK;
+
+	n = stream->total_out - bytes;
+	if (n > size)
+		n = size;
+	memcpy(buf, (char *) buffer + bytes, n);
+	bytes = n;
+	if (bytes <= size) {
+		/*
+		 * The above condition must be (bytes <= size), not
+		 * (bytes < size).  In other words, even though we
+		 * expect no more output and set avail_out to zero,
+		 * the input zlib stream may have bytes that express
+		 * "this concludes the stream", and we *do* want to
+		 * eat that input.
+		 *
+		 * Otherwise we would not be able to test that we
+		 * consumed all the input to reach the expected size;
+		 * we also want to check that zlib tells us that all
+		 * went well with status == Z_STREAM_END at the end.
+		 */
+		stream->next_out = buf + bytes;
+		stream->avail_out = size - bytes;
+		while (status == Z_OK) {
+			obj_read_unlock();
+			status = git_inflate(stream, Z_FINISH);
+			obj_read_lock();
+		}
+	}
+	if (status == Z_STREAM_END && !stream->avail_in) {
+		git_inflate_end(stream);
+		return buf;
+	}
+
+	if (status < 0)
+		error(_("corrupt loose object '%s'"), oid_to_hex(oid));
+	else if (stream->avail_in)
+		error(_("garbage at end of loose object '%s'"),
+		      oid_to_hex(oid));
+	free(buf);
+	return NULL;
+}
+
+/*
+ * We used to just use "sscanf()", but that's actually way
+ * too permissive for what we want to check. So do an anal
+ * object header parse by hand.
+ */
+static int parse_loose_header_extended(const char *hdr, struct object_info *oi,
+				       unsigned int flags)
+{
+	const char *type_buf = hdr;
+	unsigned long size;
+	int type, type_len = 0;
+
+	/*
+	 * The type can be of any size but is followed by
+	 * a space.
+	 */
+	for (;;) {
+		char c = *hdr++;
+		if (!c)
+			return -1;
+		if (c == ' ')
+			break;
+		type_len++;
+	}
+
+	type = type_from_string_gently(type_buf, type_len, 1);
+	if (oi->type_name)
+		strbuf_add(oi->type_name, type_buf, type_len);
+	/*
+	 * Set type to 0 if its an unknown object and
+	 * we're obtaining the type using '--allow-unknown-type'
+	 * option.
+	 */
+	if ((flags & OBJECT_INFO_ALLOW_UNKNOWN_TYPE) && (type < 0))
+		type = 0;
+	else if (type < 0)
+		die(_("invalid object type"));
+	if (oi->typep)
+		*oi->typep = type;
+
+	/*
+	 * The length must follow immediately, and be in canonical
+	 * decimal format (ie "010" is not valid).
+	 */
+	size = *hdr++ - '0';
+	if (size > 9)
+		return -1;
+	if (size) {
+		for (;;) {
+			unsigned long c = *hdr - '0';
+			if (c > 9)
+				break;
+			hdr++;
+			size = size * 10 + c;
+		}
+	}
+
+	if (oi->sizep)
+		*oi->sizep = size;
+
+	/*
+	 * The length must be followed by a zero byte
+	 */
+	return *hdr ? -1 : type;
+}
+
+int parse_loose_header(const char *hdr, unsigned long *sizep)
+{
+	struct object_info oi = OBJECT_INFO_INIT;
+
+	oi.sizep = sizep;
+	return parse_loose_header_extended(hdr, &oi, 0);
+}
+
+static int loose_object_info(struct repository *r,
+			     const struct object_id *oid,
+			     struct object_info *oi, int flags)
+{
+	int status = 0;
+	unsigned long mapsize;
+	void *map;
+	git_zstream stream;
+	char hdr[MAX_HEADER_LEN];
+	struct strbuf hdrbuf = STRBUF_INIT;
+	unsigned long size_scratch;
+
+	if (oi->delta_base_oid)
+		oidclr(oi->delta_base_oid);
+
+	/*
+	 * If we don't care about type or size, then we don't
+	 * need to look inside the object at all. Note that we
+	 * do not optimize out the stat call, even if the
+	 * caller doesn't care about the disk-size, since our
+	 * return value implicitly indicates whether the
+	 * object even exists.
+	 */
+	if (!oi->typep && !oi->type_name && !oi->sizep && !oi->contentp) {
+		const char *path;
+		struct stat st;
+		if (!oi->disk_sizep && (flags & OBJECT_INFO_QUICK))
+			return quick_has_loose(r, oid) ? 0 : -1;
+		if (stat_loose_object(r, oid, &st, &path) < 0)
+			return -1;
+		if (oi->disk_sizep)
+			*oi->disk_sizep = st.st_size;
+		return 0;
+	}
+
+	map = map_loose_object(r, oid, &mapsize);
+	if (!map)
+		return -1;
+
+	if (!oi->sizep)
+		oi->sizep = &size_scratch;
+
+	if (oi->disk_sizep)
+		*oi->disk_sizep = mapsize;
+	if ((flags & OBJECT_INFO_ALLOW_UNKNOWN_TYPE)) {
+		if (unpack_loose_header_to_strbuf(&stream, map, mapsize, hdr, sizeof(hdr), &hdrbuf) < 0)
+			status = error(_("unable to unpack %s header with --allow-unknown-type"),
+				       oid_to_hex(oid));
+	} else if (unpack_loose_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
+		status = error(_("unable to unpack %s header"),
+			       oid_to_hex(oid));
+	if (status < 0)
+		; /* Do nothing */
+	else if (hdrbuf.len) {
+		if ((status = parse_loose_header_extended(hdrbuf.buf, oi, flags)) < 0)
+			status = error(_("unable to parse %s header with --allow-unknown-type"),
+				       oid_to_hex(oid));
+	} else if ((status = parse_loose_header_extended(hdr, oi, flags)) < 0)
+		status = error(_("unable to parse %s header"), oid_to_hex(oid));
+
+	if (status >= 0 && oi->contentp) {
+		*oi->contentp = unpack_loose_rest(&stream, hdr,
+						  *oi->sizep, oid);
+		if (!*oi->contentp) {
+			git_inflate_end(&stream);
+			status = -1;
+		}
+	} else
+		git_inflate_end(&stream);
+
+	munmap(map, mapsize);
+	if (status && oi->typep)
+		*oi->typep = status;
+	if (oi->sizep == &size_scratch)
+		oi->sizep = NULL;
+	strbuf_release(&hdrbuf);
+	oi->whence = OI_LOOSE;
+	return (status < 0) ? status : 0;
+}
+
+int obj_read_use_lock = 0;
+pthread_mutex_t obj_read_mutex;
+
+void enable_obj_read_lock(void)
+{
+	if (obj_read_use_lock)
+		return;
+
+	obj_read_use_lock = 1;
+	init_recursive_mutex(&obj_read_mutex);
+}
+
+void disable_obj_read_lock(void)
+{
+	if (!obj_read_use_lock)
+		return;
+
+	obj_read_use_lock = 0;
+	pthread_mutex_destroy(&obj_read_mutex);
+}
+
+int fetch_if_missing = 1;
+
+static int do_oid_object_info_extended(struct repository *r,
+				       const struct object_id *oid,
+				       struct object_info *oi, unsigned flags)
+{
+	static struct object_info blank_oi = OBJECT_INFO_INIT;
+	struct cached_object *co;
+	struct pack_entry e;
+	int rtype;
+	const struct object_id *real = oid;
+	int already_retried = 0;
+
+
+	if (flags & OBJECT_INFO_LOOKUP_REPLACE)
+		real = lookup_replace_object(r, oid);
+
+	if (is_null_oid(real))
+		return -1;
+
+	if (!oi)
+		oi = &blank_oi;
+
+	co = find_cached_object(real);
+	if (co) {
+		if (oi->typep)
+			*(oi->typep) = co->type;
+		if (oi->sizep)
+			*(oi->sizep) = co->size;
+		if (oi->disk_sizep)
+			*(oi->disk_sizep) = 0;
+		if (oi->delta_base_oid)
+			oidclr(oi->delta_base_oid);
+		if (oi->type_name)
+			strbuf_addstr(oi->type_name, type_name(co->type));
+		if (oi->contentp)
+			*oi->contentp = xmemdupz(co->buf, co->size);
+		oi->whence = OI_CACHED;
+		return 0;
+	}
+
+	while (1) {
+		if (find_pack_entry(r, real, &e))
+			break;
+
+		if (flags & OBJECT_INFO_IGNORE_LOOSE)
+			return -1;
+
+		/* Most likely it's a loose object. */
+		if (!loose_object_info(r, real, oi, flags))
+			return 0;
+
+		/* Not a loose object; someone else may have just packed it. */
+		if (!(flags & OBJECT_INFO_QUICK)) {
+			reprepare_packed_git(r);
+			if (find_pack_entry(r, real, &e))
+				break;
+		}
+
+		/* Check if it is a missing object */
+		if (fetch_if_missing && has_promisor_remote() &&
+		    !already_retried && r == the_repository &&
+		    !(flags & OBJECT_INFO_SKIP_FETCH_OBJECT)) {
+			/*
+			 * TODO Investigate checking promisor_remote_get_direct()
+			 * TODO return value and stopping on error here.
+			 * TODO Pass a repository struct through
+			 * promisor_remote_get_direct(), such that arbitrary
+			 * repositories work.
+			 */
+			promisor_remote_get_direct(r, real, 1);
+			already_retried = 1;
+			continue;
+		}
+
+		return -1;
+	}
+
+	if (oi == &blank_oi)
+		/*
+		 * We know that the caller doesn't actually need the
+		 * information below, so return early.
+		 */
+		return 0;
+	rtype = packed_object_info(r, e.p, e.offset, oi);
+	if (rtype < 0) {
+		mark_bad_packed_object(e.p, real->hash);
+		return do_oid_object_info_extended(r, real, oi, 0);
+	} else if (oi->whence == OI_PACKED) {
+		oi->u.packed.offset = e.offset;
+		oi->u.packed.pack = e.p;
+		oi->u.packed.is_delta = (rtype == OBJ_REF_DELTA ||
+					 rtype == OBJ_OFS_DELTA);
+	}
+
+	return 0;
+}
+
+int oid_object_info_extended(struct repository *r, const struct object_id *oid,
+			     struct object_info *oi, unsigned flags)
+{
+	int ret;
+	obj_read_lock();
+	ret = do_oid_object_info_extended(r, oid, oi, flags);
+	obj_read_unlock();
+	return ret;
+}
+
+
+/* returns enum object_type or negative */
+int oid_object_info(struct repository *r,
+		    const struct object_id *oid,
+		    unsigned long *sizep)
+{
+	enum object_type type;
+	struct object_info oi = OBJECT_INFO_INIT;
+
+	oi.typep = &type;
+	oi.sizep = sizep;
+	if (oid_object_info_extended(r, oid, &oi,
+				      OBJECT_INFO_LOOKUP_REPLACE) < 0)
+		return -1;
+	return type;
+}
+
+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;
+}
+
+int pretend_object_file(void *buf, unsigned long len, enum object_type type,
+			struct object_id *oid)
+{
+	struct cached_object *co;
+
+	hash_object_file(the_hash_algo, buf, len, type_name(type), oid);
+	if (has_object_file_with_flags(oid, OBJECT_INFO_QUICK | OBJECT_INFO_SKIP_FETCH_OBJECT) ||
+	    find_cached_object(oid))
+		return 0;
+	ALLOC_GROW(cached_objects, cached_object_nr + 1, cached_object_alloc);
+	co = &cached_objects[cached_object_nr++];
+	co->size = len;
+	co->type = type;
+	co->buf = xmalloc(len);
+	memcpy(co->buf, buf, len);
+	oidcpy(&co->oid, oid);
+	return 0;
+}
+
+/*
+ * This function dies on corrupt objects; the callers who want to
+ * deal with them should arrange to call read_object() and give error
+ * messages themselves.
+ */
+void *read_object_file_extended(struct repository *r,
+				const struct object_id *oid,
+				enum object_type *type,
+				unsigned long *size,
+				int lookup_replace)
+{
+	void *data;
+	const struct packed_git *p;
+	const char *path;
+	struct stat st;
+	const struct object_id *repl = lookup_replace ?
+		lookup_replace_object(r, oid) : oid;
+
+	errno = 0;
+	data = read_object(r, repl, type, size);
+	if (data)
+		return data;
+
+	obj_read_lock();
+	if (errno && errno != ENOENT)
+		die_errno(_("failed to read object %s"), oid_to_hex(oid));
+
+	/* die if we replaced an object with one that does not exist */
+	if (repl != oid)
+		die(_("replacement %s not found for %s"),
+		    oid_to_hex(repl), oid_to_hex(oid));
+
+	if (!stat_loose_object(r, repl, &st, &path))
+		die(_("loose object %s (stored in %s) is corrupt"),
+		    oid_to_hex(repl), path);
+
+	if ((p = has_packed_and_bad(r, repl->hash)) != NULL)
+		die(_("packed object %s (stored in %s) is corrupt"),
+		    oid_to_hex(repl), p->pack_name);
+	obj_read_unlock();
+
+	return NULL;
+}
+
+void *read_object_with_reference(struct repository *r,
+				 const struct object_id *oid,
+				 const char *required_type_name,
+				 unsigned long *size,
+				 struct object_id *actual_oid_return)
+{
+	enum object_type type, required_type;
+	void *buffer;
+	unsigned long isize;
+	struct object_id actual_oid;
+
+	required_type = type_from_string(required_type_name);
+	oidcpy(&actual_oid, oid);
+	while (1) {
+		int ref_length = -1;
+		const char *ref_type = NULL;
+
+		buffer = repo_read_object_file(r, &actual_oid, &type, &isize);
+		if (!buffer)
+			return NULL;
+		if (type == required_type) {
+			*size = isize;
+			if (actual_oid_return)
+				oidcpy(actual_oid_return, &actual_oid);
+			return buffer;
+		}
+		/* Handle references */
+		else if (type == OBJ_COMMIT)
+			ref_type = "tree ";
+		else if (type == OBJ_TAG)
+			ref_type = "object ";
+		else {
+			free(buffer);
+			return NULL;
+		}
+		ref_length = strlen(ref_type);
+
+		if (ref_length + the_hash_algo->hexsz > isize ||
+		    memcmp(buffer, ref_type, ref_length) ||
+		    get_oid_hex((char *) buffer + ref_length, &actual_oid)) {
+			free(buffer);
+			return NULL;
+		}
+		free(buffer);
+		/* Now we have the ID of the referred-to object in
+		 * actual_oid.  Check again. */
+	}
+}
+
+static void write_object_file_prepare(const struct git_hash_algo *algo,
+				      const void *buf, unsigned long len,
+				      const char *type, struct object_id *oid,
+				      char *hdr, int *hdrlen)
+{
+	git_hash_ctx c;
+
+	/* Generate the header */
+	*hdrlen = xsnprintf(hdr, *hdrlen, "%s %"PRIuMAX , type, (uintmax_t)len)+1;
+
+	/* Sha1.. */
+	algo->init_fn(&c);
+	algo->update_fn(&c, hdr, *hdrlen);
+	algo->update_fn(&c, buf, len);
+	algo->final_fn(oid->hash, &c);
+}
+
+/*
+ * Move the just written object into its final resting place.
+ */
+int finalize_object_file(const char *tmpfile, const char *filename)
+{
+	int ret = 0;
+
+	if (object_creation_mode == OBJECT_CREATION_USES_RENAMES)
+		goto try_rename;
+	else if (link(tmpfile, filename))
+		ret = errno;
+
+	/*
+	 * Coda hack - coda doesn't like cross-directory links,
+	 * so we fall back to a rename, which will mean that it
+	 * won't be able to check collisions, but that's not a
+	 * big deal.
+	 *
+	 * The same holds for FAT formatted media.
+	 *
+	 * When this succeeds, we just return.  We have nothing
+	 * left to unlink.
+	 */
+	if (ret && ret != EEXIST) {
+	try_rename:
+		if (!rename(tmpfile, filename))
+			goto out;
+		ret = errno;
+	}
+	unlink_or_warn(tmpfile);
+	if (ret) {
+		if (ret != EEXIST) {
+			return error_errno(_("unable to write file %s"), filename);
+		}
+		/* FIXME!!! Collision check here ? */
+	}
+
+out:
+	if (adjust_shared_perm(filename))
+		return error(_("unable to set permission to '%s'"), filename);
+	return 0;
+}
+
+static int write_buffer(int fd, const void *buf, size_t len)
+{
+	if (write_in_full(fd, buf, len) < 0)
+		return error_errno(_("file write error"));
+	return 0;
+}
+
+int hash_object_file(const struct git_hash_algo *algo, const void *buf,
+		     unsigned long len, const char *type,
+		     struct object_id *oid)
+{
+	char hdr[MAX_HEADER_LEN];
+	int hdrlen = sizeof(hdr);
+	write_object_file_prepare(algo, buf, len, type, oid, hdr, &hdrlen);
+	return 0;
+}
+
+/* Finalize a file on disk, and close it. */
+static void close_loose_object(int fd)
+{
+	if (fsync_object_files)
+		fsync_or_die(fd, "loose object file");
+	if (close(fd) != 0)
+		die_errno(_("error when closing loose object file"));
+}
+
+/* Size of directory component, including the ending '/' */
+static inline int directory_size(const char *filename)
+{
+	const char *s = strrchr(filename, '/');
+	if (!s)
+		return 0;
+	return s - filename + 1;
+}
+
+/*
+ * This creates a temporary file in the same directory as the final
+ * 'filename'
+ *
+ * We want to avoid cross-directory filename renames, because those
+ * can have problems on various filesystems (FAT, NFS, Coda).
+ */
+static int create_tmpfile(struct strbuf *tmp, const char *filename)
+{
+	int fd, dirlen = directory_size(filename);
+
+	strbuf_reset(tmp);
+	strbuf_add(tmp, filename, dirlen);
+	strbuf_addstr(tmp, "tmp_obj_XXXXXX");
+	fd = git_mkstemp_mode(tmp->buf, 0444);
+	if (fd < 0 && dirlen && errno == ENOENT) {
+		/*
+		 * Make sure the directory exists; note that the contents
+		 * of the buffer are undefined after mkstemp returns an
+		 * error, so we have to rewrite the whole buffer from
+		 * scratch.
+		 */
+		strbuf_reset(tmp);
+		strbuf_add(tmp, filename, dirlen - 1);
+		if (mkdir(tmp->buf, 0777) && errno != EEXIST)
+			return -1;
+		if (adjust_shared_perm(tmp->buf))
+			return -1;
+
+		/* Try again */
+		strbuf_addstr(tmp, "/tmp_obj_XXXXXX");
+		fd = git_mkstemp_mode(tmp->buf, 0444);
+	}
+	return fd;
+}
+
+static int write_loose_object(const struct object_id *oid, char *hdr,
+			      int hdrlen, const void *buf, unsigned long len,
+			      time_t mtime)
+{
+	int fd, ret;
+	unsigned char compressed[4096];
+	git_zstream stream;
+	git_hash_ctx c;
+	struct object_id parano_oid;
+	static struct strbuf tmp_file = STRBUF_INIT;
+	static struct strbuf filename = STRBUF_INIT;
+
+	loose_object_path(the_repository, &filename, oid);
+
+	fd = create_tmpfile(&tmp_file, filename.buf);
+	if (fd < 0) {
+		if (errno == EACCES)
+			return error(_("insufficient permission for adding an object to repository database %s"), get_object_directory());
+		else
+			return error_errno(_("unable to create temporary file"));
+	}
+
+	/* Set it up */
+	git_deflate_init(&stream, zlib_compression_level);
+	stream.next_out = compressed;
+	stream.avail_out = sizeof(compressed);
+	the_hash_algo->init_fn(&c);
+
+	/* First header.. */
+	stream.next_in = (unsigned char *)hdr;
+	stream.avail_in = hdrlen;
+	while (git_deflate(&stream, 0) == Z_OK)
+		; /* nothing */
+	the_hash_algo->update_fn(&c, hdr, hdrlen);
+
+	/* Then the data itself.. */
+	stream.next_in = (void *)buf;
+	stream.avail_in = len;
+	do {
+		unsigned char *in0 = stream.next_in;
+		ret = git_deflate(&stream, Z_FINISH);
+		the_hash_algo->update_fn(&c, in0, stream.next_in - in0);
+		if (write_buffer(fd, compressed, stream.next_out - compressed) < 0)
+			die(_("unable to write loose object file"));
+		stream.next_out = compressed;
+		stream.avail_out = sizeof(compressed);
+	} while (ret == Z_OK);
+
+	if (ret != Z_STREAM_END)
+		die(_("unable to deflate new object %s (%d)"), oid_to_hex(oid),
+		    ret);
+	ret = git_deflate_end_gently(&stream);
+	if (ret != Z_OK)
+		die(_("deflateEnd on object %s failed (%d)"), oid_to_hex(oid),
+		    ret);
+	the_hash_algo->final_fn(parano_oid.hash, &c);
+	if (!oideq(oid, &parano_oid))
+		die(_("confused by unstable object source data for %s"),
+		    oid_to_hex(oid));
+
+	close_loose_object(fd);
+
+	if (mtime) {
+		struct utimbuf utb;
+		utb.actime = mtime;
+		utb.modtime = mtime;
+		if (utime(tmp_file.buf, &utb) < 0)
+			warning_errno(_("failed utime() on %s"), tmp_file.buf);
+	}
+
+	return finalize_object_file(tmp_file.buf, filename.buf);
+}
+
+static int freshen_loose_object(const struct object_id *oid)
+{
+	return check_and_freshen(oid, 1);
+}
+
+static int freshen_packed_object(const struct object_id *oid)
+{
+	struct pack_entry e;
+	if (!find_pack_entry(the_repository, oid, &e))
+		return 0;
+	if (e.p->freshened)
+		return 1;
+	if (!freshen_file(e.p->pack_name))
+		return 0;
+	e.p->freshened = 1;
+	return 1;
+}
+
+int write_object_file(const void *buf, unsigned long len, const char *type,
+		      struct object_id *oid)
+{
+	char hdr[MAX_HEADER_LEN];
+	int hdrlen = sizeof(hdr);
+
+	/* Normally if we have it in the pack then we do not bother writing
+	 * it out into .git/objects/??/?{38} file.
+	 */
+	write_object_file_prepare(the_hash_algo, buf, len, type, oid, hdr,
+				  &hdrlen);
+	if (freshen_packed_object(oid) || freshen_loose_object(oid))
+		return 0;
+	return write_loose_object(oid, hdr, hdrlen, buf, len, 0);
+}
+
+int hash_object_file_literally(const void *buf, unsigned long len,
+			       const char *type, struct object_id *oid,
+			       unsigned flags)
+{
+	char *header;
+	int hdrlen, status = 0;
+
+	/* type string, SP, %lu of the length plus NUL must fit this */
+	hdrlen = strlen(type) + MAX_HEADER_LEN;
+	header = xmalloc(hdrlen);
+	write_object_file_prepare(the_hash_algo, buf, len, type, oid, header,
+				  &hdrlen);
+
+	if (!(flags & HASH_WRITE_OBJECT))
+		goto cleanup;
+	if (freshen_packed_object(oid) || freshen_loose_object(oid))
+		goto cleanup;
+	status = write_loose_object(oid, header, hdrlen, buf, len, 0);
+
+cleanup:
+	free(header);
+	return status;
+}
+
+int force_object_loose(const struct object_id *oid, time_t mtime)
+{
+	void *buf;
+	unsigned long len;
+	enum object_type type;
+	char hdr[MAX_HEADER_LEN];
+	int hdrlen;
+	int ret;
+
+	if (has_loose_object(oid))
+		return 0;
+	buf = read_object(the_repository, oid, &type, &len);
+	if (!buf)
+		return error(_("cannot read object for %s"), oid_to_hex(oid));
+	hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %"PRIuMAX , type_name(type), (uintmax_t)len) + 1;
+	ret = write_loose_object(oid, hdr, hdrlen, buf, len, mtime);
+	free(buf);
+
+	return ret;
+}
+
+int has_object(struct repository *r, const struct object_id *oid,
+	       unsigned flags)
+{
+	int quick = !(flags & HAS_OBJECT_RECHECK_PACKED);
+	unsigned object_info_flags = OBJECT_INFO_SKIP_FETCH_OBJECT |
+		(quick ? OBJECT_INFO_QUICK : 0);
+
+	if (!startup_info->have_repository)
+		return 0;
+	return oid_object_info_extended(r, oid, NULL, object_info_flags) >= 0;
+}
+
+int repo_has_object_file_with_flags(struct repository *r,
+				    const struct object_id *oid, int flags)
+{
+	if (!startup_info->have_repository)
+		return 0;
+	return oid_object_info_extended(r, oid, NULL, flags) >= 0;
+}
+
+int repo_has_object_file(struct repository *r,
+			 const struct object_id *oid)
+{
+	return repo_has_object_file_with_flags(r, oid, 0);
+}
+
+static void check_tree(const void *buf, size_t size)
+{
+	struct tree_desc desc;
+	struct name_entry entry;
+
+	init_tree_desc(&desc, buf, size);
+	while (tree_entry(&desc, &entry))
+		/* do nothing
+		 * tree_entry() will die() on malformed entries */
+		;
+}
+
+static void check_commit(const void *buf, size_t size)
+{
+	struct commit c;
+	memset(&c, 0, sizeof(c));
+	if (parse_commit_buffer(the_repository, &c, buf, size, 0))
+		die(_("corrupt commit"));
+}
+
+static void check_tag(const void *buf, size_t size)
+{
+	struct tag t;
+	memset(&t, 0, sizeof(t));
+	if (parse_tag_buffer(the_repository, &t, buf, size))
+		die(_("corrupt tag"));
+}
+
+static int index_mem(struct index_state *istate,
+		     struct object_id *oid, void *buf, size_t size,
+		     enum object_type type,
+		     const char *path, unsigned flags)
+{
+	int ret, re_allocated = 0;
+	int write_object = flags & HASH_WRITE_OBJECT;
+
+	if (!type)
+		type = OBJ_BLOB;
+
+	/*
+	 * Convert blobs to git internal format
+	 */
+	if ((type == OBJ_BLOB) && path) {
+		struct strbuf nbuf = STRBUF_INIT;
+		if (convert_to_git(istate, path, buf, size, &nbuf,
+				   get_conv_flags(flags))) {
+			buf = strbuf_detach(&nbuf, &size);
+			re_allocated = 1;
+		}
+	}
+	if (flags & HASH_FORMAT_CHECK) {
+		if (type == OBJ_TREE)
+			check_tree(buf, size);
+		if (type == OBJ_COMMIT)
+			check_commit(buf, size);
+		if (type == OBJ_TAG)
+			check_tag(buf, size);
+	}
+
+	if (write_object)
+		ret = write_object_file(buf, size, type_name(type), oid);
+	else
+		ret = hash_object_file(the_hash_algo, buf, size,
+				       type_name(type), oid);
+	if (re_allocated)
+		free(buf);
+	return ret;
+}
+
+static int index_stream_convert_blob(struct index_state *istate,
+				     struct object_id *oid,
+				     int fd,
+				     const char *path,
+				     unsigned flags)
+{
+	int ret;
+	const int write_object = flags & HASH_WRITE_OBJECT;
+	struct strbuf sbuf = STRBUF_INIT;
+
+	assert(path);
+	assert(would_convert_to_git_filter_fd(istate, path));
+
+	convert_to_git_filter_fd(istate, path, fd, &sbuf,
+				 get_conv_flags(flags));
+
+	if (write_object)
+		ret = write_object_file(sbuf.buf, sbuf.len, type_name(OBJ_BLOB),
+					oid);
+	else
+		ret = hash_object_file(the_hash_algo, sbuf.buf, sbuf.len,
+				       type_name(OBJ_BLOB), oid);
+	strbuf_release(&sbuf);
+	return ret;
+}
+
+static int index_pipe(struct index_state *istate, struct object_id *oid,
+		      int fd, enum object_type type,
+		      const char *path, unsigned flags)
+{
+	struct strbuf sbuf = STRBUF_INIT;
+	int ret;
+
+	if (strbuf_read(&sbuf, fd, 4096) >= 0)
+		ret = index_mem(istate, oid, sbuf.buf, sbuf.len, type, path, flags);
+	else
+		ret = -1;
+	strbuf_release(&sbuf);
+	return ret;
+}
+
+#define SMALL_FILE_SIZE (32*1024)
+
+static int index_core(struct index_state *istate,
+		      struct object_id *oid, int fd, size_t size,
+		      enum object_type type, const char *path,
+		      unsigned flags)
+{
+	int ret;
+
+	if (!size) {
+		ret = index_mem(istate, oid, "", size, type, path, flags);
+	} else if (size <= SMALL_FILE_SIZE) {
+		char *buf = xmalloc(size);
+		ssize_t read_result = read_in_full(fd, buf, size);
+		if (read_result < 0)
+			ret = error_errno(_("read error while indexing %s"),
+					  path ? path : "<unknown>");
+		else if (read_result != size)
+			ret = error(_("short read while indexing %s"),
+				    path ? path : "<unknown>");
+		else
+			ret = index_mem(istate, oid, buf, size, type, path, flags);
+		free(buf);
+	} else {
+		void *buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+		ret = index_mem(istate, oid, buf, size, type, path, flags);
+		munmap(buf, size);
+	}
+	return ret;
+}
+
+/*
+ * This creates one packfile per large blob unless bulk-checkin
+ * machinery is "plugged".
+ *
+ * This also bypasses the usual "convert-to-git" dance, and that is on
+ * purpose. We could write a streaming version of the converting
+ * functions and insert that before feeding the data to fast-import
+ * (or equivalent in-core API described above). However, that is
+ * somewhat complicated, as we do not know the size of the filter
+ * result, which we need to know beforehand when writing a git object.
+ * Since the primary motivation for trying to stream from the working
+ * tree file and to avoid mmaping it in core is to deal with large
+ * binary blobs, they generally do not want to get any conversion, and
+ * callers should avoid this code path when filters are requested.
+ */
+static int index_stream(struct object_id *oid, int fd, size_t size,
+			enum object_type type, const char *path,
+			unsigned flags)
+{
+	return index_bulk_checkin(oid, fd, size, type, path, flags);
+}
+
+int index_fd(struct index_state *istate, struct object_id *oid,
+	     int fd, struct stat *st,
+	     enum object_type type, const char *path, unsigned flags)
+{
+	int ret;
+
+	/*
+	 * Call xsize_t() only when needed to avoid potentially unnecessary
+	 * die() for large files.
+	 */
+	if (type == OBJ_BLOB && path && would_convert_to_git_filter_fd(istate, path))
+		ret = index_stream_convert_blob(istate, oid, fd, path, flags);
+	else if (!S_ISREG(st->st_mode))
+		ret = index_pipe(istate, oid, fd, type, path, flags);
+	else if (st->st_size <= big_file_threshold || type != OBJ_BLOB ||
+		 (path && would_convert_to_git(istate, path)))
+		ret = index_core(istate, oid, fd, xsize_t(st->st_size),
+				 type, path, flags);
+	else
+		ret = index_stream(oid, fd, xsize_t(st->st_size), type, path,
+				   flags);
+	close(fd);
+	return ret;
+}
+
+int index_path(struct index_state *istate, struct object_id *oid,
+	       const char *path, struct stat *st, unsigned flags)
+{
+	int fd;
+	struct strbuf sb = STRBUF_INIT;
+	int rc = 0;
+
+	switch (st->st_mode & S_IFMT) {
+	case S_IFREG:
+		fd = open(path, O_RDONLY);
+		if (fd < 0)
+			return error_errno("open(\"%s\")", path);
+		if (index_fd(istate, oid, fd, st, OBJ_BLOB, path, flags) < 0)
+			return error(_("%s: failed to insert into database"),
+				     path);
+		break;
+	case S_IFLNK:
+		if (strbuf_readlink(&sb, path, st->st_size))
+			return error_errno("readlink(\"%s\")", path);
+		if (!(flags & HASH_WRITE_OBJECT))
+			hash_object_file(the_hash_algo, sb.buf, sb.len,
+					 blob_type, oid);
+		else if (write_object_file(sb.buf, sb.len, blob_type, oid))
+			rc = error(_("%s: failed to insert into database"), path);
+		strbuf_release(&sb);
+		break;
+	case S_IFDIR:
+		return resolve_gitlink_ref(path, "HEAD", oid);
+	default:
+		return error(_("%s: unsupported file type"), path);
+	}
+	return rc;
+}
+
+int read_pack_header(int fd, struct pack_header *header)
+{
+	if (read_in_full(fd, header, sizeof(*header)) != sizeof(*header))
+		/* "eof before pack header was fully read" */
+		return PH_ERROR_EOF;
+
+	if (header->hdr_signature != htonl(PACK_SIGNATURE))
+		/* "protocol error (pack signature mismatch detected)" */
+		return PH_ERROR_PACK_SIGNATURE;
+	if (!pack_version_ok(header->hdr_version))
+		/* "protocol error (pack version unsupported)" */
+		return PH_ERROR_PROTOCOL;
+	return 0;
+}
+
+void assert_oid_type(const struct object_id *oid, enum object_type expect)
+{
+	enum object_type type = oid_object_info(the_repository, oid, NULL);
+	if (type < 0)
+		die(_("%s is not a valid object"), oid_to_hex(oid));
+	if (type != expect)
+		die(_("%s is not a valid '%s' object"), oid_to_hex(oid),
+		    type_name(expect));
+}
+
+int for_each_file_in_obj_subdir(unsigned int subdir_nr,
+				struct strbuf *path,
+				each_loose_object_fn obj_cb,
+				each_loose_cruft_fn cruft_cb,
+				each_loose_subdir_fn subdir_cb,
+				void *data)
+{
+	size_t origlen, baselen;
+	DIR *dir;
+	struct dirent *de;
+	int r = 0;
+	struct object_id oid;
+
+	if (subdir_nr > 0xff)
+		BUG("invalid loose object subdirectory: %x", subdir_nr);
+
+	origlen = path->len;
+	strbuf_complete(path, '/');
+	strbuf_addf(path, "%02x", subdir_nr);
+
+	dir = opendir(path->buf);
+	if (!dir) {
+		if (errno != ENOENT)
+			r = error_errno(_("unable to open %s"), path->buf);
+		strbuf_setlen(path, origlen);
+		return r;
+	}
+
+	oid.hash[0] = subdir_nr;
+	strbuf_addch(path, '/');
+	baselen = path->len;
+
+	while ((de = readdir(dir))) {
+		size_t namelen;
+		if (is_dot_or_dotdot(de->d_name))
+			continue;
+
+		namelen = strlen(de->d_name);
+		strbuf_setlen(path, baselen);
+		strbuf_add(path, de->d_name, namelen);
+		if (namelen == the_hash_algo->hexsz - 2 &&
+		    !hex_to_bytes(oid.hash + 1, de->d_name,
+				  the_hash_algo->rawsz - 1)) {
+			if (obj_cb) {
+				r = obj_cb(&oid, path->buf, data);
+				if (r)
+					break;
+			}
+			continue;
+		}
+
+		if (cruft_cb) {
+			r = cruft_cb(de->d_name, path->buf, data);
+			if (r)
+				break;
+		}
+	}
+	closedir(dir);
+
+	strbuf_setlen(path, baselen - 1);
+	if (!r && subdir_cb)
+		r = subdir_cb(subdir_nr, path->buf, data);
+
+	strbuf_setlen(path, origlen);
+
+	return r;
+}
+
+int for_each_loose_file_in_objdir_buf(struct strbuf *path,
+			    each_loose_object_fn obj_cb,
+			    each_loose_cruft_fn cruft_cb,
+			    each_loose_subdir_fn subdir_cb,
+			    void *data)
+{
+	int r = 0;
+	int i;
+
+	for (i = 0; i < 256; i++) {
+		r = for_each_file_in_obj_subdir(i, path, obj_cb, cruft_cb,
+						subdir_cb, data);
+		if (r)
+			break;
+	}
+
+	return r;
+}
+
+int for_each_loose_file_in_objdir(const char *path,
+				  each_loose_object_fn obj_cb,
+				  each_loose_cruft_fn cruft_cb,
+				  each_loose_subdir_fn subdir_cb,
+				  void *data)
+{
+	struct strbuf buf = STRBUF_INIT;
+	int r;
+
+	strbuf_addstr(&buf, path);
+	r = for_each_loose_file_in_objdir_buf(&buf, obj_cb, cruft_cb,
+					      subdir_cb, data);
+	strbuf_release(&buf);
+
+	return r;
+}
+
+int for_each_loose_object(each_loose_object_fn cb, void *data,
+			  enum for_each_object_flags flags)
+{
+	struct object_directory *odb;
+
+	prepare_alt_odb(the_repository);
+	for (odb = the_repository->objects->odb; odb; odb = odb->next) {
+		int r = for_each_loose_file_in_objdir(odb->path, cb, NULL,
+						      NULL, data);
+		if (r)
+			return r;
+
+		if (flags & FOR_EACH_OBJECT_LOCAL_ONLY)
+			break;
+	}
+
+	return 0;
+}
+
+static int append_loose_object(const struct object_id *oid, const char *path,
+			       void *data)
+{
+	oid_array_append(data, oid);
+	return 0;
+}
+
+struct oid_array *odb_loose_cache(struct object_directory *odb,
+				  const struct object_id *oid)
+{
+	int subdir_nr = oid->hash[0];
+	struct strbuf buf = STRBUF_INIT;
+
+	if (subdir_nr < 0 ||
+	    subdir_nr >= ARRAY_SIZE(odb->loose_objects_subdir_seen))
+		BUG("subdir_nr out of range");
+
+	if (odb->loose_objects_subdir_seen[subdir_nr])
+		return &odb->loose_objects_cache[subdir_nr];
+
+	strbuf_addstr(&buf, odb->path);
+	for_each_file_in_obj_subdir(subdir_nr, &buf,
+				    append_loose_object,
+				    NULL, NULL,
+				    &odb->loose_objects_cache[subdir_nr]);
+	odb->loose_objects_subdir_seen[subdir_nr] = 1;
+	strbuf_release(&buf);
+	return &odb->loose_objects_cache[subdir_nr];
+}
+
+void odb_clear_loose_cache(struct object_directory *odb)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(odb->loose_objects_cache); i++)
+		oid_array_clear(&odb->loose_objects_cache[i]);
+	memset(&odb->loose_objects_subdir_seen, 0,
+	       sizeof(odb->loose_objects_subdir_seen));
+}
+
+static int check_stream_oid(git_zstream *stream,
+			    const char *hdr,
+			    unsigned long size,
+			    const char *path,
+			    const struct object_id *expected_oid)
+{
+	git_hash_ctx c;
+	struct object_id real_oid;
+	unsigned char buf[4096];
+	unsigned long total_read;
+	int status = Z_OK;
+
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&c, hdr, stream->total_out);
+
+	/*
+	 * We already read some bytes into hdr, but the ones up to the NUL
+	 * do not count against the object's content size.
+	 */
+	total_read = stream->total_out - strlen(hdr) - 1;
+
+	/*
+	 * This size comparison must be "<=" to read the final zlib packets;
+	 * see the comment in unpack_loose_rest for details.
+	 */
+	while (total_read <= size &&
+	       (status == Z_OK ||
+		(status == Z_BUF_ERROR && !stream->avail_out))) {
+		stream->next_out = buf;
+		stream->avail_out = sizeof(buf);
+		if (size - total_read < stream->avail_out)
+			stream->avail_out = size - total_read;
+		status = git_inflate(stream, Z_FINISH);
+		the_hash_algo->update_fn(&c, buf, stream->next_out - buf);
+		total_read += stream->next_out - buf;
+	}
+	git_inflate_end(stream);
+
+	if (status != Z_STREAM_END) {
+		error(_("corrupt loose object '%s'"), oid_to_hex(expected_oid));
+		return -1;
+	}
+	if (stream->avail_in) {
+		error(_("garbage at end of loose object '%s'"),
+		      oid_to_hex(expected_oid));
+		return -1;
+	}
+
+	the_hash_algo->final_fn(real_oid.hash, &c);
+	if (!oideq(expected_oid, &real_oid)) {
+		error(_("hash mismatch for %s (expected %s)"), path,
+		      oid_to_hex(expected_oid));
+		return -1;
+	}
+
+	return 0;
+}
+
+int read_loose_object(const char *path,
+		      const struct object_id *expected_oid,
+		      enum object_type *type,
+		      unsigned long *size,
+		      void **contents)
+{
+	int ret = -1;
+	void *map = NULL;
+	unsigned long mapsize;
+	git_zstream stream;
+	char hdr[MAX_HEADER_LEN];
+
+	*contents = NULL;
+
+	map = map_loose_object_1(the_repository, path, NULL, &mapsize);
+	if (!map) {
+		error_errno(_("unable to mmap %s"), path);
+		goto out;
+	}
+
+	if (unpack_loose_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0) {
+		error(_("unable to unpack header of %s"), path);
+		goto out;
+	}
+
+	*type = parse_loose_header(hdr, size);
+	if (*type < 0) {
+		error(_("unable to parse header of %s"), path);
+		git_inflate_end(&stream);
+		goto out;
+	}
+
+	if (*type == OBJ_BLOB && *size > big_file_threshold) {
+		if (check_stream_oid(&stream, hdr, *size, path, expected_oid) < 0)
+			goto out;
+	} else {
+		*contents = unpack_loose_rest(&stream, hdr, *size, expected_oid);
+		if (!*contents) {
+			error(_("unable to unpack contents of %s"), path);
+			git_inflate_end(&stream);
+			goto out;
+		}
+		if (check_object_signature(the_repository, expected_oid,
+					   *contents, *size,
+					   type_name(*type))) {
+			error(_("hash mismatch for %s (expected %s)"), path,
+			      oid_to_hex(expected_oid));
+			free(*contents);
+			goto out;
+		}
+	}
+
+	ret = 0; /* everything checks out */
+
+out:
+	if (map)
+		munmap(map, mapsize);
+	return ret;
+}