1 files changed, 340 insertions, 251 deletions

diff --git a/sha1_file.c b/sha1_file.c
index d0f2aa029b..266152de36 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -23,6 +23,9 @@
 #include "bulk-checkin.h"
 #include "streaming.h"
 #include "dir.h"
+#include "mru.h"
+#include "list.h"
+#include "mergesort.h"
 
 #ifndef O_NOATIME
 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
@@ -37,6 +40,12 @@ static inline uintmax_t sz_fmt(size_t s) { return s; }
 
 const unsigned char null_sha1[20];
 const struct object_id null_oid;
+const struct object_id empty_tree_oid = {
+	EMPTY_TREE_SHA1_BIN_LITERAL
+};
+const struct object_id empty_blob_oid = {
+	EMPTY_BLOB_SHA1_BIN_LITERAL
+};
 
 /*
  * This is meant to hold a *small* number of objects that you would
@@ -59,14 +68,6 @@ static struct cached_object empty_tree = {
 	0
 };
 
-/*
- * A pointer to the last packed_git in which an object was found.
- * When an object is sought, we look in this packfile first, because
- * objects that are looked up at similar times are often in the same
- * packfile as one another.
- */
-static struct packed_git *last_found_pack;
-
 static struct cached_object *find_cached_object(const unsigned char *sha1)
 {
 	int i;
@@ -171,36 +172,42 @@ enum scld_error safe_create_leading_directories_const(const char *path)
 	return result;
 }
 
-static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
+static void fill_sha1_path(struct strbuf *buf, const unsigned char *sha1)
 {
 	int i;
 	for (i = 0; i < 20; i++) {
 		static char hex[] = "0123456789abcdef";
 		unsigned int val = sha1[i];
-		char *pos = pathbuf + i*2 + (i > 0);
-		*pos++ = hex[val >> 4];
-		*pos = hex[val & 0xf];
+		strbuf_addch(buf, hex[val >> 4]);
+		strbuf_addch(buf, hex[val & 0xf]);
+		if (!i)
+			strbuf_addch(buf, '/');
 	}
 }
 
 const char *sha1_file_name(const unsigned char *sha1)
 {
-	static char buf[PATH_MAX];
-	const char *objdir;
-	int len;
+	static struct strbuf buf = STRBUF_INIT;
 
-	objdir = get_object_directory();
-	len = strlen(objdir);
+	strbuf_reset(&buf);
+	strbuf_addf(&buf, "%s/", get_object_directory());
 
-	/* '/' + sha1(2) + '/' + sha1(38) + '\0' */
-	if (len + 43 > PATH_MAX)
-		die("insanely long object directory %s", objdir);
-	memcpy(buf, objdir, len);
-	buf[len] = '/';
-	buf[len+3] = '/';
-	buf[len+42] = '\0';
-	fill_sha1_path(buf + len + 1, sha1);
-	return buf;
+	fill_sha1_path(&buf, sha1);
+	return buf.buf;
+}
+
+struct strbuf *alt_scratch_buf(struct alternate_object_database *alt)
+{
+	strbuf_setlen(&alt->scratch, alt->base_len);
+	return &alt->scratch;
+}
+
+static const char *alt_sha1_path(struct alternate_object_database *alt,
+				 const unsigned char *sha1)
+{
+	struct strbuf *buf = alt_scratch_buf(alt);
+	fill_sha1_path(buf, sha1);
+	return buf->buf;
 }
 
 /*
@@ -234,6 +241,35 @@ struct alternate_object_database *alt_odb_list;
 static struct alternate_object_database **alt_odb_tail;
 
 /*
+ * Return non-zero iff the path is usable as an alternate object database.
+ */
+static int alt_odb_usable(struct strbuf *path, const char *normalized_objdir)
+{
+	struct alternate_object_database *alt;
+
+	/* 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 (alt = alt_odb_list; alt; alt = alt->next) {
+		if (!fspathcmp(path->buf, alt->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
@@ -252,8 +288,6 @@ static int link_alt_odb_entry(const char *entry, const char *relative_base,
 	int depth, const char *normalized_objdir)
 {
 	struct alternate_object_database *ent;
-	struct alternate_object_database *alt;
-	size_t pfxlen, entlen;
 	struct strbuf pathbuf = STRBUF_INIT;
 
 	if (!is_absolute_path(entry) && relative_base) {
@@ -262,49 +296,26 @@ static int link_alt_odb_entry(const char *entry, const char *relative_base,
 	}
 	strbuf_addstr(&pathbuf, entry);
 
-	normalize_path_copy(pathbuf.buf, pathbuf.buf);
-
-	pfxlen = strlen(pathbuf.buf);
+	if (strbuf_normalize_path(&pathbuf) < 0) {
+		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 (pfxlen && pathbuf.buf[pfxlen-1] == '/')
-		pfxlen -= 1;
-
-	entlen = st_add(pfxlen, 43); /* '/' + 2 hex + '/' + 38 hex + NUL */
-	ent = xmalloc(st_add(sizeof(*ent), entlen));
-	memcpy(ent->base, pathbuf.buf, pfxlen);
-	strbuf_release(&pathbuf);
+	while (pathbuf.len && pathbuf.buf[pathbuf.len - 1] == '/')
+		strbuf_setlen(&pathbuf, pathbuf.len - 1);
 
-	ent->name = ent->base + pfxlen + 1;
-	ent->base[pfxlen + 3] = '/';
-	ent->base[pfxlen] = ent->base[entlen-1] = 0;
-
-	/* Detect cases where alternate disappeared */
-	if (!is_directory(ent->base)) {
-		error("object directory %s does not exist; "
-		      "check .git/objects/info/alternates.",
-		      ent->base);
-		free(ent);
+	if (!alt_odb_usable(&pathbuf, normalized_objdir)) {
+		strbuf_release(&pathbuf);
 		return -1;
 	}
 
-	/* Prevent the common mistake of listing the same
-	 * thing twice, or object directory itself.
-	 */
-	for (alt = alt_odb_list; alt; alt = alt->next) {
-		if (pfxlen == alt->name - alt->base - 1 &&
-		    !memcmp(ent->base, alt->base, pfxlen)) {
-			free(ent);
-			return -1;
-		}
-	}
-	if (!strcmp_icase(ent->base, normalized_objdir)) {
-		free(ent);
-		return -1;
-	}
+	ent = alloc_alt_odb(pathbuf.buf);
 
 	/* add the alternate entry */
 	*alt_odb_tail = ent;
@@ -312,10 +323,9 @@ static int link_alt_odb_entry(const char *entry, const char *relative_base,
 	ent->next = NULL;
 
 	/* recursively add alternates */
-	read_info_alternates(ent->base, depth + 1);
-
-	ent->base[pfxlen] = '/';
+	read_info_alternates(pathbuf.buf, depth + 1);
 
+	strbuf_release(&pathbuf);
 	return 0;
 }
 
@@ -334,7 +344,9 @@ static void link_alt_odb_entries(const char *alt, int len, int sep,
 	}
 
 	strbuf_add_absolute_path(&objdirbuf, get_object_directory());
-	normalize_path_copy(objdirbuf.buf, objdirbuf.buf);
+	if (strbuf_normalize_path(&objdirbuf) < 0)
+		die("unable to normalize object directory: %s",
+		    objdirbuf.buf);
 
 	alt_copy = xmemdupz(alt, len);
 	string_list_split_in_place(&entries, alt_copy, sep, -1);
@@ -342,12 +354,7 @@ static void link_alt_odb_entries(const char *alt, int len, int sep,
 		const char *entry = entries.items[i].string;
 		if (entry[0] == '\0' || entry[0] == '#')
 			continue;
-		if (!is_absolute_path(entry) && depth) {
-			error("%s: ignoring relative alternate object store %s",
-					relative_base, entry);
-		} else {
-			link_alt_odb_entry(entry, relative_base, depth, objdirbuf.buf);
-		}
+		link_alt_odb_entry(entry, relative_base, depth, objdirbuf.buf);
 	}
 	string_list_clear(&entries, 0);
 	free(alt_copy);
@@ -380,6 +387,18 @@ void read_info_alternates(const char * relative_base, int depth)
 	munmap(map, mapsz);
 }
 
+struct alternate_object_database *alloc_alt_odb(const char *dir)
+{
+	struct alternate_object_database *ent;
+
+	FLEX_ALLOC_STR(ent, path, dir);
+	strbuf_init(&ent->scratch, 0);
+	strbuf_addf(&ent->scratch, "%s/", dir);
+	ent->base_len = ent->scratch.len;
+
+	return ent;
+}
+
 void add_to_alternates_file(const char *reference)
 {
 	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
@@ -425,6 +444,93 @@ void add_to_alternates_file(const char *reference)
 	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();
+
+	link_alt_odb_entries(reference, strlen(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 $GITDIR.
+ * `err` must not be null.
+ */
+char *compute_alternate_path(const char *path, struct strbuf *err)
+{
+	char *ref_git = NULL;
+	const char *repo, *ref_git_s;
+	int seen_error = 0;
+
+	ref_git_s = real_path_if_valid(path);
+	if (!ref_git_s) {
+		seen_error = 1;
+		strbuf_addf(err, _("path '%s' does not exist"), path);
+		goto out;
+	} else
+		/*
+		 * Beware: read_gitfile(), real_path() and mkpath()
+		 * return static buffer
+		 */
+		ref_git = xstrdup(ref_git_s);
+
+	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(ref_git);
+		ref_git = NULL;
+	}
+
+	return ref_git;
+}
+
 int foreach_alt_odb(alt_odb_fn fn, void *cb)
 {
 	struct alternate_object_database *ent;
@@ -489,8 +595,8 @@ static int check_and_freshen_nonlocal(const unsigned char *sha1, int freshen)
 	struct alternate_object_database *alt;
 	prepare_alt_odb();
 	for (alt = alt_odb_list; alt; alt = alt->next) {
-		fill_sha1_path(alt->name, sha1);
-		if (check_and_freshen_file(alt->base, freshen))
+		const char *path = alt_sha1_path(alt, sha1);
+		if (check_and_freshen_file(path, freshen))
 			return 1;
 	}
 	return 0;
@@ -522,6 +628,9 @@ static size_t peak_pack_mapped;
 static size_t pack_mapped;
 struct packed_git *packed_git;
 
+static struct mru packed_git_mru_storage;
+struct mru *packed_git_mru = &packed_git_mru_storage;
+
 void pack_report(void)
 {
 	fprintf(stderr,
@@ -795,7 +904,7 @@ void close_all_packs(void)
 
 	for (p = packed_git; p; p = p->next)
 		if (p->do_not_close)
-			die("BUG! Want to close pack marked 'do-not-close'");
+			die("BUG: want to close pack marked 'do-not-close'");
 		else
 			close_pack(p);
 }
@@ -891,36 +1000,6 @@ void close_pack_index(struct packed_git *p)
 	}
 }
 
-/*
- * This is used by git-repack in case a newly created pack happens to
- * contain the same set of objects as an existing one.  In that case
- * the resulting file might be different even if its name would be the
- * same.  It is best to close any reference to the old pack before it is
- * replaced on disk.  Of course no index pointers or windows for given pack
- * must subsist at this point.  If ever objects from this pack are requested
- * again, the new version of the pack will be reinitialized through
- * reprepare_packed_git().
- */
-void free_pack_by_name(const char *pack_name)
-{
-	struct packed_git *p, **pp = &packed_git;
-
-	while (*pp) {
-		p = *pp;
-		if (strcmp(pack_name, p->pack_name) == 0) {
-			clear_delta_base_cache();
-			close_pack(p);
-			free(p->bad_object_sha1);
-			*pp = p->next;
-			if (last_found_pack == p)
-				last_found_pack = NULL;
-			free(p);
-			return;
-		}
-		pp = &p->next;
-	}
-}
-
 static unsigned int get_max_fd_limit(void)
 {
 #ifdef RLIMIT_NOFILE
@@ -1107,9 +1186,8 @@ unsigned char *use_pack(struct packed_git *p,
 				PROT_READ, MAP_PRIVATE,
 				p->pack_fd, win->offset);
 			if (win->base == MAP_FAILED)
-				die("packfile %s cannot be mapped: %s",
-					p->pack_name,
-					strerror(errno));
+				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);
@@ -1279,8 +1357,8 @@ static void prepare_packed_git_one(char *objdir, int local)
 	dir = opendir(path.buf);
 	if (!dir) {
 		if (errno != ENOENT)
-			error("unable to open object pack directory: %s: %s",
-			      path.buf, strerror(errno));
+			error_errno("unable to open object pack directory: %s",
+				    path.buf);
 		strbuf_release(&path);
 		return;
 	}
@@ -1332,10 +1410,20 @@ static void prepare_packed_git_one(char *objdir, int local)
 	strbuf_release(&path);
 }
 
+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_)
 {
-	struct packed_git *a = *((struct packed_git **)a_);
-	struct packed_git *b = *((struct packed_git **)b_);
+	const struct packed_git *a = a_;
+	const struct packed_git *b = b_;
 	int st;
 
 	/*
@@ -1362,28 +1450,17 @@ static int sort_pack(const void *a_, const void *b_)
 
 static void rearrange_packed_git(void)
 {
-	struct packed_git **ary, *p;
-	int i, n;
-
-	for (n = 0, p = packed_git; p; p = p->next)
-		n++;
-	if (n < 2)
-		return;
-
-	/* prepare an array of packed_git for easier sorting */
-	ary = xcalloc(n, sizeof(struct packed_git *));
-	for (n = 0, p = packed_git; p; p = p->next)
-		ary[n++] = p;
-
-	qsort(ary, n, sizeof(struct packed_git *), sort_pack);
+	packed_git = llist_mergesort(packed_git, get_next_packed_git,
+				     set_next_packed_git, sort_pack);
+}
 
-	/* link them back again */
-	for (i = 0; i < n - 1; i++)
-		ary[i]->next = ary[i + 1];
-	ary[n - 1]->next = NULL;
-	packed_git = ary[0];
+static void prepare_packed_git_mru(void)
+{
+	struct packed_git *p;
 
-	free(ary);
+	mru_clear(packed_git_mru);
+	for (p = packed_git; p; p = p->next)
+		mru_append(packed_git_mru, p);
 }
 
 static int prepare_packed_git_run_once = 0;
@@ -1395,12 +1472,10 @@ void prepare_packed_git(void)
 		return;
 	prepare_packed_git_one(get_object_directory(), 1);
 	prepare_alt_odb();
-	for (alt = alt_odb_list; alt; alt = alt->next) {
-		alt->name[-1] = 0;
-		prepare_packed_git_one(alt->base, 0);
-		alt->name[-1] = '/';
-	}
+	for (alt = alt_odb_list; alt; alt = alt->next)
+		prepare_packed_git_one(alt->path, 0);
 	rearrange_packed_git();
+	prepare_packed_git_mru();
 	prepare_packed_git_run_once = 1;
 }
 
@@ -1516,8 +1591,8 @@ static int stat_sha1_file(const unsigned char *sha1, struct stat *st)
 	prepare_alt_odb();
 	errno = ENOENT;
 	for (alt = alt_odb_list; alt; alt = alt->next) {
-		fill_sha1_path(alt->name, sha1);
-		if (!lstat(alt->base, st))
+		const char *path = alt_sha1_path(alt, sha1);
+		if (!lstat(path, st))
 			return 0;
 	}
 
@@ -1537,8 +1612,8 @@ static int open_sha1_file(const unsigned char *sha1)
 
 	prepare_alt_odb();
 	for (alt = alt_odb_list; alt; alt = alt->next) {
-		fill_sha1_path(alt->name, sha1);
-		fd = git_open_noatime(alt->base);
+		const char *path = alt_sha1_path(alt, sha1);
+		fd = git_open_noatime(path);
 		if (fd >= 0)
 			return fd;
 		if (most_interesting_errno == ENOENT)
@@ -1597,7 +1672,9 @@ unsigned long unpack_object_header_buffer(const unsigned char *buf,
 	return used;
 }
 
-int unpack_sha1_header(git_zstream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
+static int unpack_sha1_short_header(git_zstream *stream,
+				    unsigned char *map, unsigned long mapsize,
+				    void *buffer, unsigned long bufsiz)
 {
 	/* Get the data stream */
 	memset(stream, 0, sizeof(*stream));
@@ -1610,13 +1687,31 @@ int unpack_sha1_header(git_zstream *stream, unsigned char *map, unsigned long ma
 	return git_inflate(stream, 0);
 }
 
+int unpack_sha1_header(git_zstream *stream,
+		       unsigned char *map, unsigned long mapsize,
+		       void *buffer, unsigned long bufsiz)
+{
+	int status = unpack_sha1_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_sha1_header_to_strbuf(git_zstream *stream, unsigned char *map,
 					unsigned long mapsize, void *buffer,
 					unsigned long bufsiz, struct strbuf *header)
 {
 	int status;
 
-	status = unpack_sha1_header(stream, map, mapsize, buffer, bufsiz);
+	status = unpack_sha1_short_header(stream, map, mapsize, buffer, bufsiz);
+	if (status < Z_OK)
+		return -1;
 
 	/*
 	 * Check if entire header is unpacked in the first iteration.
@@ -1707,6 +1802,8 @@ static int parse_sha1_header_extended(const char *hdr, struct object_info *oi,
 	 */
 	for (;;) {
 		char c = *hdr++;
+		if (!c)
+			return -1;
 		if (c == ' ')
 			break;
 		type_len++;
@@ -1717,7 +1814,7 @@ static int parse_sha1_header_extended(const char *hdr, struct object_info *oi,
 		strbuf_add(oi->typename, type_buf, type_len);
 	/*
 	 * Set type to 0 if its an unknown object and
-	 * we're obtaining the type using '--allow-unkown-type'
+	 * we're obtaining the type using '--allow-unknown-type'
 	 * option.
 	 */
 	if ((flags & LOOKUP_UNKNOWN_OBJECT) && (type < 0))
@@ -1755,11 +1852,9 @@ static int parse_sha1_header_extended(const char *hdr, struct object_info *oi,
 
 int parse_sha1_header(const char *hdr, unsigned long *sizep)
 {
-	struct object_info oi;
+	struct object_info oi = OBJECT_INFO_INIT;
 
 	oi.sizep = sizep;
-	oi.typename = NULL;
-	oi.typep = NULL;
 	return parse_sha1_header_extended(hdr, &oi, LOOKUP_REPLACE_OBJECT);
 }
 
@@ -1997,8 +2092,8 @@ unwind:
 	goto out;
 }
 
-static int packed_object_info(struct packed_git *p, off_t obj_offset,
-			      struct object_info *oi)
+int packed_object_info(struct packed_git *p, off_t obj_offset,
+		       struct object_info *oi)
 {
 	struct pack_window *w_curs = NULL;
 	unsigned long size;
@@ -2098,136 +2193,142 @@ static void *unpack_compressed_entry(struct packed_git *p,
 	return buffer;
 }
 
-#define MAX_DELTA_CACHE (256)
-
+static struct hashmap delta_base_cache;
 static size_t delta_base_cached;
 
-static struct delta_base_cache_lru_list {
-	struct delta_base_cache_lru_list *prev;
-	struct delta_base_cache_lru_list *next;
-} delta_base_cache_lru = { &delta_base_cache_lru, &delta_base_cache_lru };
+static LIST_HEAD(delta_base_cache_lru);
 
-static struct delta_base_cache_entry {
-	struct delta_base_cache_lru_list lru;
-	void *data;
+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;
-} delta_base_cache[MAX_DELTA_CACHE];
+};
 
-static unsigned long pack_entry_hash(struct packed_git *p, off_t base_offset)
+static unsigned int pack_entry_hash(struct packed_git *p, off_t base_offset)
 {
-	unsigned long hash;
+	unsigned int hash;
 
-	hash = (unsigned long)(intptr_t)p + (unsigned long)base_offset;
+	hash = (unsigned int)(intptr_t)p + (unsigned int)base_offset;
 	hash += (hash >> 8) + (hash >> 16);
-	return hash % MAX_DELTA_CACHE;
+	return hash;
 }
 
 static struct delta_base_cache_entry *
 get_delta_base_cache_entry(struct packed_git *p, off_t base_offset)
 {
-	unsigned long hash = pack_entry_hash(p, base_offset);
-	return delta_base_cache + hash;
+	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 eq_delta_base_cache_entry(struct delta_base_cache_entry *ent,
-				     struct packed_git *p, off_t base_offset)
+static int delta_base_cache_hash_cmp(const void *va, const void *vb,
+				     const void *vkey)
 {
-	return (ent->data && ent->p == p && ent->base_offset == base_offset);
+	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)
 {
-	struct delta_base_cache_entry *ent;
-	ent = get_delta_base_cache_entry(p, base_offset);
-	return eq_delta_base_cache_entry(ent, p, base_offset);
+	return !!get_delta_base_cache_entry(p, base_offset);
 }
 
-static void clear_delta_base_cache_entry(struct delta_base_cache_entry *ent)
+/*
+ * 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)
 {
-	ent->data = NULL;
-	ent->lru.next->prev = ent->lru.prev;
-	ent->lru.prev->next = ent->lru.next;
+	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 packed_git *p, off_t base_offset,
-	unsigned long *base_size, enum object_type *type, int keep_cache)
+	unsigned long *base_size, enum object_type *type)
 {
 	struct delta_base_cache_entry *ent;
-	void *ret;
 
 	ent = get_delta_base_cache_entry(p, base_offset);
-
-	if (!eq_delta_base_cache_entry(ent, p, base_offset))
+	if (!ent)
 		return unpack_entry(p, base_offset, type, base_size);
 
-	ret = ent->data;
-
-	if (!keep_cache)
-		clear_delta_base_cache_entry(ent);
-	else
-		ret = xmemdupz(ent->data, ent->size);
 	*type = ent->type;
 	*base_size = ent->size;
-	return ret;
+	return xmemdupz(ent->data, ent->size);
 }
 
 static inline void release_delta_base_cache(struct delta_base_cache_entry *ent)
 {
-	if (ent->data) {
-		free(ent->data);
-		ent->data = NULL;
-		ent->lru.next->prev = ent->lru.prev;
-		ent->lru.prev->next = ent->lru.next;
-		delta_base_cached -= ent->size;
-	}
+	free(ent->data);
+	detach_delta_base_cache_entry(ent);
 }
 
 void clear_delta_base_cache(void)
 {
-	unsigned long p;
-	for (p = 0; p < MAX_DELTA_CACHE; p++)
-		release_delta_base_cache(&delta_base_cache[p]);
+	struct hashmap_iter iter;
+	struct delta_base_cache_entry *entry;
+	for (entry = hashmap_iter_first(&delta_base_cache, &iter);
+	     entry;
+	     entry = hashmap_iter_next(&iter)) {
+		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)
 {
-	unsigned long hash = pack_entry_hash(p, base_offset);
-	struct delta_base_cache_entry *ent = delta_base_cache + hash;
-	struct delta_base_cache_lru_list *lru;
+	struct delta_base_cache_entry *ent = xmalloc(sizeof(*ent));
+	struct list_head *lru, *tmp;
 
-	release_delta_base_cache(ent);
 	delta_base_cached += base_size;
 
-	for (lru = delta_base_cache_lru.next;
-	     delta_base_cached > delta_base_cache_limit
-	     && lru != &delta_base_cache_lru;
-	     lru = lru->next) {
-		struct delta_base_cache_entry *f = (void *)lru;
-		if (f->type == OBJ_BLOB)
-			release_delta_base_cache(f);
-	}
-	for (lru = delta_base_cache_lru.next;
-	     delta_base_cached > delta_base_cache_limit
-	     && lru != &delta_base_cache_lru;
-	     lru = lru->next) {
-		struct delta_base_cache_entry *f = (void *)lru;
+	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->p = p;
-	ent->base_offset = base_offset;
+	ent->key.p = p;
+	ent->key.base_offset = base_offset;
 	ent->type = type;
 	ent->data = base;
 	ent->size = base_size;
-	ent->lru.next = &delta_base_cache_lru;
-	ent->lru.prev = delta_base_cache_lru.prev;
-	delta_base_cache_lru.prev->next = &ent->lru;
-	delta_base_cache_lru.prev = &ent->lru;
+	list_add_tail(&ent->lru, &delta_base_cache_lru);
+
+	if (!delta_base_cache.cmpfn)
+		hashmap_init(&delta_base_cache, delta_base_cache_hash_cmp, 0);
+	hashmap_entry_init(ent, pack_entry_hash(p, base_offset));
+	hashmap_add(&delta_base_cache, ent);
 }
 
 static void *read_object(const unsigned char *sha1, enum object_type *type,
@@ -2271,18 +2372,18 @@ void *unpack_entry(struct packed_git *p, off_t obj_offset,
 		struct delta_base_cache_entry *ent;
 
 		ent = get_delta_base_cache_entry(p, curpos);
-		if (eq_delta_base_cache_entry(ent, p, curpos)) {
+		if (ent) {
 			type = ent->type;
 			data = ent->data;
 			size = ent->size;
-			clear_delta_base_cache_entry(ent);
+			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);
-			unsigned long len = revidx[1].offset - obj_offset;
+			off_t len = revidx[1].offset - obj_offset;
 			if (check_pack_crc(p, &w_curs, obj_offset, len, revidx->nr)) {
 				const unsigned char *sha1 =
 					nth_packed_object_sha1(p, revidx->nr);
@@ -2331,7 +2432,7 @@ void *unpack_entry(struct packed_git *p, off_t obj_offset,
 	case OBJ_OFS_DELTA:
 	case OBJ_REF_DELTA:
 		if (data)
-			die("BUG in unpack_entry: left loop at a valid delta");
+			die("BUG: unpack_entry: left loop at a valid delta");
 		break;
 	case OBJ_COMMIT:
 	case OBJ_TREE:
@@ -2605,21 +2706,15 @@ static int fill_pack_entry(const unsigned char *sha1,
  */
 static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
 {
-	struct packed_git *p;
+	struct mru_entry *p;
 
 	prepare_packed_git();
 	if (!packed_git)
 		return 0;
 
-	if (last_found_pack && fill_pack_entry(sha1, e, last_found_pack))
-		return 1;
-
-	for (p = packed_git; p; p = p->next) {
-		if (p == last_found_pack)
-			continue; /* we already checked this one */
-
-		if (fill_pack_entry(sha1, e, p)) {
-			last_found_pack = p;
+	for (p = packed_git_mru->head; p; p = p->next) {
+		if (fill_pack_entry(sha1, e, p->item)) {
+			mru_mark(packed_git_mru, p);
 			return 1;
 		}
 	}
@@ -2769,7 +2864,7 @@ int sha1_object_info_extended(const unsigned char *sha1, struct object_info *oi,
 int sha1_object_info(const unsigned char *sha1, unsigned long *sizep)
 {
 	enum object_type type;
-	struct object_info oi = {NULL};
+	struct object_info oi = OBJECT_INFO_INIT;
 
 	oi.typep = &type;
 	oi.sizep = sizep;
@@ -2786,7 +2881,7 @@ static void *read_packed_sha1(const unsigned char *sha1,
 
 	if (!find_pack_entry(sha1, &e))
 		return NULL;
-	data = cache_or_unpack_entry(e.p, e.offset, size, type, 1);
+	data = cache_or_unpack_entry(e.p, e.offset, size, type);
 	if (!data) {
 		/*
 		 * We're probably in deep shit, but let's try to fetch
@@ -2984,7 +3079,7 @@ int finalize_object_file(const char *tmpfile, const char *filename)
 	unlink_or_warn(tmpfile);
 	if (ret) {
 		if (ret != EEXIST) {
-			return error("unable to write sha1 filename %s: %s", filename, strerror(ret));
+			return error_errno("unable to write sha1 filename %s", filename);
 		}
 		/* FIXME!!! Collision check here ? */
 	}
@@ -2998,7 +3093,7 @@ out:
 static int write_buffer(int fd, const void *buf, size_t len)
 {
 	if (write_in_full(fd, buf, len) < 0)
-		return error("file write error (%s)", strerror(errno));
+		return error_errno("file write error");
 	return 0;
 }
 
@@ -3081,7 +3176,7 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 		if (errno == EACCES)
 			return error("insufficient permission for adding an object to repository database %s", get_object_directory());
 		else
-			return error("unable to create temporary file: %s", strerror(errno));
+			return error_errno("unable to create temporary file");
 	}
 
 	/* Set it up */
@@ -3126,8 +3221,7 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 		utb.actime = mtime;
 		utb.modtime = mtime;
 		if (utime(tmp_file.buf, &utb) < 0)
-			warning("failed utime() on %s: %s",
-				tmp_file.buf, strerror(errno));
+			warning_errno("failed utime() on %s", tmp_file.buf);
 	}
 
 	return finalize_object_file(tmp_file.buf, filename);
@@ -3360,7 +3454,7 @@ static int index_core(unsigned char *sha1, int fd, size_t size,
 		if (size == read_in_full(fd, buf, size))
 			ret = index_mem(sha1, buf, size, type, path, flags);
 		else
-			ret = error("short read %s", strerror(errno));
+			ret = error_errno("short read");
 		free(buf);
 	} else {
 		void *buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
@@ -3425,18 +3519,14 @@ int index_path(unsigned char *sha1, const char *path, struct stat *st, unsigned
 	case S_IFREG:
 		fd = open(path, O_RDONLY);
 		if (fd < 0)
-			return error("open(\"%s\"): %s", path,
-				     strerror(errno));
+			return error_errno("open(\"%s\")", path);
 		if (index_fd(sha1, 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)) {
-			char *errstr = strerror(errno);
-			return error("readlink(\"%s\"): %s", path,
-			             errstr);
-		}
+		if (strbuf_readlink(&sb, path, st->st_size))
+			return error_errno("readlink(\"%s\")", path);
 		if (!(flags & HASH_WRITE_OBJECT))
 			hash_sha1_file(sb.buf, sb.len, blob_type, sha1);
 		else if (write_sha1_file(sb.buf, sb.len, blob_type, sha1))
@@ -3492,7 +3582,7 @@ static int for_each_file_in_obj_subdir(int subdir_nr,
 	if (!dir) {
 		if (errno == ENOENT)
 			return 0;
-		return error("unable to open %s: %s", path->buf, strerror(errno));
+		return error_errno("unable to open %s", path->buf);
 	}
 
 	while ((de = readdir(dir))) {
@@ -3584,8 +3674,7 @@ static int loose_from_alt_odb(struct alternate_object_database *alt,
 	struct strbuf buf = STRBUF_INIT;
 	int r;
 
-	/* copy base not including trailing '/' */
-	strbuf_add(&buf, alt->base, alt->name - alt->base - 1);
+	strbuf_addstr(&buf, alt->path);
 	r = for_each_loose_file_in_objdir_buf(&buf,
 					      data->cb, NULL, NULL,
 					      data->data);