[PATCH] Remove "delta" object representation.

Packed delta files created by git-pack-objects seems to be the
way to go, and existing "delta" object handling code has exposed
the object representation details to too many places.  Remove it
while we refactor code to come up with a proper interface in
sha1_file.c.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/git-fsck-cache.txt

@@ -9,7 +9,7 @@ git-fsck-cache - Verifies the connectivity and validity of the objects in the da
 SYNOPSIS
 --------
-'git-fsck-cache' [--tags] [--root] [--delta-depth] [--unreachable] [--cache] [<object>*]
+'git-fsck-cache' [--tags] [--root] [--unreachable] [--cache] [<object>*]
 DESCRIPTION
 -----------
@@ -37,9 +37,6 @@ OPTIONS
 	Consider any object recorded in the cache also as a head node for
 	an unreachability trace.
---delta-depth::
-	Report back the length of the longest delta chain found.
-
 It tests SHA1 and general object sanity, and it does full tracking of
 the resulting reachability and everything else. It prints out any
 corruption it finds (missing or bad objects), and if you use the

Documentation/git-http-pull.txt

@@ -21,13 +21,6 @@ Downloads a remote GIT repository via HTTP.
 	Get trees associated with the commit objects.
 -a::
 	Get all the objects.
--d::
-	Do not check for delta base objects (use this option
-	only when you know the remote repository is not
-	deltified).
---recover::
-	Check dependency of deltified object more carefully than
-	usual, to recover after earlier pull that was interrupted.
 -v::
 	Report what is downloaded.
 -w::

Documentation/git-local-pull.txt

@@ -23,13 +23,6 @@ OPTIONS
 	Get trees associated with the commit objects.
 -a::
 	Get all the objects.
--d::
-	Do not check for delta base objects (use this option
-	only when you know the remote repository is not
-	deltified).
---recover::
-	Check dependency of deltified object more carefully than
-	usual, to recover after earlier pull that was interrupted.
 -v::
 	Report what is downloaded.
 -w::

Documentation/git-mkdelta.txt

-git-mkdelta(1)
-==============
-May 2005
-
-NAME
-----
-git-mkdelta - Creates a delta object
-
-
-SYNOPSIS
---------
-'git-mkdelta' [-v] [-d N | --max-depth=N ] <reference_object> <target_object> [ <next_object> ... ]
-
-DESCRIPTION
------------
-Creates a delta object to replace <reference_object> by using an
-ordered list of potential objects to deltafy against earlier objects
-in the list.
-
-A cap on the depth of delta references can be provided as well,
-otherwise the default is to not have any limit.  A limit of 0 will
-also undeltafy a given object.
-
-
-OPTIONS
--------
--v::
-	Verbose
-
--d|--max-depth::
-	limit the number of delta references in a chain
-	If 0 then all objects are undeltafied.
-	
-Author
-------
-Git is written by Linus Torvalds <torvalds@osdl.org> and the git-list <git@vger.kernel.org>.
-
-Documentation
---------------
-Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>.
-
-GIT
----
-Part of the link:git.html[git] suite
-

Documentation/git-ssh-pull.txt

@@ -31,13 +31,6 @@ commit-id::
 	Get trees associated with the commit objects.
 -a::
 	Get all the objects.
--d::
-	Do not check for delta base objects (use this option
-	only when you know the remote repository is not
-	deltified).
---recover::
-	Check dependency of deltified object more carefully than
-	usual, to recover after earlier pull that was interrupted.
 -v::
 	Report what is downloaded.
 -w::

Documentation/git-ssh-push.txt

@@ -28,13 +28,6 @@ commit-id::
         Get tree associated with the requested commit object.
 -a::
         Get all the objects.
--d::
-        Do not check for delta base objects (use this option
-        only when you know the local repository is not
-        deltified).
---recover::
-        Check dependency of deltified object more carefully than
-        usual, to recover after earlier push that was interrupted.
 -v::
         Report what is uploaded.
 -w::

Documentation/git.txt

@@ -51,9 +51,6 @@ link:git-init-db.html[git-init-db]::
 link:git-merge-base.html[git-merge-base]::
 	Finds as good a common ancestor as possible for a merge
-link:git-mkdelta.html[git-mkdelta]::
-	Creates a delta object
-
 link:git-mktag.html[git-mktag]::
 	Creates a tag object

Makefile

@@ -22,7 +22,7 @@ INSTALL=install
 SCRIPTS=git git-apply-patch-script git-merge-one-file-script git-prune-script \
 	git-pull-script git-tag-script git-resolve-script git-whatchanged \
-	git-deltafy-script git-fetch-script git-status-script git-commit-script \
+	git-fetch-script git-status-script git-commit-script \
 	git-log-script git-shortlog git-cvsimport-script git-diff-script \
 	git-reset-script git-add-script git-checkout-script git-clone-script \
 	gitk git-cherry git-rebase-script git-relink-script
@@ -34,7 +34,7 @@ PROG=   git-update-cache git-diff-files git-init-db git-write-tree \
 	git-unpack-file git-export git-diff-cache git-convert-cache \
 	git-http-pull git-ssh-push git-ssh-pull git-rev-list git-mktag \
 	git-diff-helper git-tar-tree git-local-pull git-write-blob \
-	git-get-tar-commit-id git-mkdelta git-apply git-stripspace \
+	git-get-tar-commit-id git-apply git-stripspace \
 	git-cvs2git git-diff-stages git-rev-parse git-patch-id \
 	git-pack-objects git-unpack-objects
@@ -44,7 +44,7 @@ install: $(PROG) $(SCRIPTS)
 	$(INSTALL) $(PROG) $(SCRIPTS) $(dest)$(bin)
 LIB_OBJS=read-cache.o sha1_file.o usage.o object.o commit.o tree.o blob.o \
-	 tag.o delta.o date.o index.o diff-delta.o patch-delta.o entry.o \
+	 tag.o date.o index.o diff-delta.o patch-delta.o entry.o \
 	 epoch.o refs.o csum-file.o
 LIB_FILE=libgit.a
 LIB_H=cache.h object.h blob.h tree.h commit.h tag.h delta.h epoch.h csum-file.h
@@ -117,7 +117,6 @@ git-mktag: mktag.c
 git-diff-helper: diff-helper.c
 git-tar-tree: tar-tree.c
 git-write-blob: write-blob.c
-git-mkdelta: mkdelta.c
 git-stripspace: stripspace.c
 git-cvs2git: cvs2git.c
 git-diff-stages: diff-stages.c

README

@@ -32,8 +32,8 @@ build up a hierarchy of objects.
 All objects have a statically determined "type" aka "tag", which is
 determined at object creation time, and which identifies the format of
 the object (i.e. how it is used, and how it can refer to other
-objects).  There are currently five different object types: "blob",
-"tree", "commit", "tag" and "delta"
+objects).  There are currently four different object types: "blob",
+"tree", "commit" and "tag".
 A "blob" object cannot refer to any other object, and is, like the tag
 implies, a pure storage object containing some user data.  It is used to
@@ -62,16 +62,12 @@ A "tag" object symbolically identifies and can be used to sign other
 objects. It contains the identifier and type of another object, a
 symbolic name (of course!) and, optionally, a signature.
-A "delta" object is used internally by the object database to minimise
-disk usage. Instead of storing the entire contents of a revision, git
-can behave in a similar manner to RCS et al and simply store a delta.
-
 Regardless of object type, all objects share the following
 characteristics: they are all deflated with zlib, and have a header
 that not only specifies their tag, but also provides size information
 about the data in the object.  It's worth noting that the SHA1 hash
-that is used to name the object is the hash of the original data or
-the delta. (Historical note: in the dawn of the age of git the hash
+that is used to name the object is the hash of the original data.
+(Historical note: in the dawn of the age of git the hash
 was the sha1 of the _compressed_ object)
 As a result, the general consistency of an object can always be tested
@@ -219,29 +215,6 @@ verification) has to come from outside.
 A tag is created with link:git-mktag.html[git-mktag] and
 it's data can be accessed by link:git-cat-file.html[git-cat-file]
-Delta Object
-~~~~~~~~~~~~
-
-The "delta" object is used internally by the object database to
-minimise storage usage by using xdeltas (byte level diffs). Deltas can
-form chains of arbitrary length as RCS does (although this is
-configureable at creation time). Most operations won't see or even be
-aware of delta objects as they are automatically 'applied' and appear
-as 'real' git objects In other words, if you write your own routines
-to look at the contents of the object database then you need to know
-about this - otherwise you don't. Actually, that's not quite true -
-one important area where deltas are likely to prove very valuable is
-in reducing bandwidth loads - so the more sophisticated network tools
-for git repositories will be aware of them too.
-
-Finally, git repositories can (and must) be deltafied in the
-background - the work to calculate the differences does not take place
-automatically at commit time.
-
-A delta can be created (or undeltafied) with
-link:git-mkdelta.html[git-mkdelta] it's raw data cannot be accessed at
-present.
-
 The "index" aka "Current Directory Cache"
 -----------------------------------------

cache.h

@@ -162,7 +162,6 @@ extern char *sha1_file_name(const unsigned char *sha1);
 extern void * map_sha1_file(const unsigned char *sha1, unsigned long *size);
 extern int unpack_sha1_header(z_stream *stream, void *map, unsigned long mapsize, void *buffer, unsigned long size);
 extern int parse_sha1_header(char *hdr, char *type, unsigned long *sizep);
-extern int sha1_delta_base(const unsigned char *, unsigned char *);
 extern int sha1_file_size(const unsigned char *, unsigned long *);
 extern void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size);
 extern void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size);

delta.c

-#include "object.h"
-#include "blob.h"
-#include "tree.h"
-#include "commit.h"
-#include "tag.h"
-#include "delta.h"
-#include "cache.h"
-
-/* the delta object definition (it can alias any other object) */
-struct delta {
-	union {
-		struct object object;
-		struct blob blob;
-		struct tree tree;
-		struct commit commit;
-		struct tag tag;
-	} u;
-};
-
-struct delta *lookup_delta(const unsigned char *sha1)
-{
-	struct object *obj = lookup_object(sha1);
-	if (!obj) {
-		struct delta *ret = xmalloc(sizeof(struct delta));
-		memset(ret, 0, sizeof(struct delta));
-		created_object(sha1, &ret->u.object);
-		return ret;
-	}
-	return (struct delta *) obj;
-}
-
-int parse_delta_buffer(struct delta *item, void *buffer, unsigned long size)
-{
-	struct object *reference;
-	struct object_list *p;
-
-	if (item->u.object.delta)
-		return 0;
-	item->u.object.delta = 1;
-	if (size <= 20)
-		return -1;
-	reference = lookup_object(buffer);
-	if (!reference) {
-		struct delta *ref = xmalloc(sizeof(struct delta));
-		memset(ref, 0, sizeof(struct delta));
-		created_object(buffer, &ref->u.object);
-		reference = &ref->u.object;
-	}
-
-	p = xmalloc(sizeof(*p));
-	p->item = &item->u.object;
-	p->next = reference->attached_deltas;
-	reference->attached_deltas = p;
-	return 0;
-}
-
-int process_deltas(void *src, unsigned long src_size, const char *src_type,
-		   struct object_list *delta_list)
-{
-	int deepest = 0;
-	do {
-		struct object *obj = delta_list->item;
-		static char type[10];
-		void *map, *delta, *buf;
-		unsigned long map_size, delta_size, buf_size;
-		map = map_sha1_file(obj->sha1, &map_size);
-		if (!map)
-			continue;
-		delta = unpack_sha1_file(map, map_size, type, &delta_size);
-		munmap(map, map_size);
-		if (!delta)
-			continue;
-		if (strcmp(type, "delta") || delta_size <= 20) {
-			free(delta);
-			continue;
-		}
-		buf = patch_delta(src, src_size,
-				  delta+20, delta_size-20,
-				  &buf_size);
-		free(delta);
-		if (!buf)
-			continue;
-		if (check_sha1_signature(obj->sha1, buf, buf_size, src_type) < 0)
-			printf("sha1 mismatch for delta %s\n", sha1_to_hex(obj->sha1));
-		if (obj->type && obj->type != src_type) {
-			error("got %s when expecting %s for delta %s",
-			      src_type, obj->type, sha1_to_hex(obj->sha1));
-			free(buf);
-			continue;
-		}
-		obj->type = src_type;
-		if (src_type == blob_type) {
-			parse_blob_buffer((struct blob *)obj, buf, buf_size);
-		} else if (src_type == tree_type) {
-			parse_tree_buffer((struct tree *)obj, buf, buf_size);
-		} else if (src_type == commit_type) {
-			parse_commit_buffer((struct commit *)obj, buf, buf_size);
-		} else if (src_type == tag_type) {
-			parse_tag_buffer((struct tag *)obj, buf, buf_size);
-		} else {
-			error("unknown object type %s", src_type);
-			free(buf);
-			continue;
-		}
-		if (obj->attached_deltas) {
-			int depth = process_deltas(buf, buf_size, src_type,
-						   obj->attached_deltas);
-			if (deepest < depth)
-				deepest = depth;
-		}
-		free(buf);
-	} while ((delta_list = delta_list->next));
-	return deepest + 1;
-}

delta.h

@@ -9,13 +9,4 @@ extern void *patch_delta(void *src_buf, unsigned long src_size,
 			 void *delta_buf, unsigned long delta_size,
 			 unsigned long *dst_size);
-/* handling of delta objects */
-struct delta;
-struct object_list;
-extern struct delta *lookup_delta(const unsigned char *sha1);
-extern int parse_delta_buffer(struct delta *item, void *buffer, unsigned long size);
-extern int parse_delta(struct delta *item, unsigned char sha1);
-extern int process_deltas(void *src, unsigned long src_size,
-			  const char *src_type, struct object_list *delta);
-
 #endif

fsck-cache.c

@@ -6,46 +6,15 @@
 #include "tree.h"
 #include "blob.h"
 #include "tag.h"
-#include "delta.h"
 #define REACHABLE 0x0001
 static int show_root = 0;
 static int show_tags = 0;
 static int show_unreachable = 0;
-static int show_max_delta_depth = 0;
 static int keep_cache_objects = 0; 
 static unsigned char head_sha1[20];
-static void expand_deltas(void)
-{
-	int i, max_depth = 0;
-
-	/*
-	 * To be as efficient as possible we look for delta heads and
-	 * recursively process them going backward, and parsing
-	 * resulting objects along the way.  This allows for processing
-	 * each delta objects only once regardless of the delta depth.
-	 */
-	for (i = 0; i < nr_objs; i++) {
-		struct object *obj = objs[i];
-		if (obj->parsed && !obj->delta && obj->attached_deltas) {
-			int depth = 0;
-			char type[10];
-			unsigned long size;
-			void *buf = read_sha1_file(obj->sha1, type, &size);
-			if (!buf)
-				continue;
-			depth = process_deltas(buf, size, obj->type,
-					       obj->attached_deltas);
-			if (max_depth < depth)
-				max_depth = depth;
-		}
-	}
-	if (show_max_delta_depth)
-		printf("maximum delta depth = %d\n", max_depth);
-}
-															
 static void check_connectivity(void)
 {
 	int i;
@@ -56,12 +25,8 @@ static void check_connectivity(void)
 		struct object_list *refs;
 		if (!obj->parsed) {
-			if (obj->delta)
-				printf("unresolved delta %s\n",
-				       sha1_to_hex(obj->sha1));
-			else
-				printf("missing %s %s\n",
-				       obj->type, sha1_to_hex(obj->sha1));
+			printf("missing %s %s\n",
+			       obj->type, sha1_to_hex(obj->sha1));
 			continue;
 		}
@@ -75,12 +40,8 @@ static void check_connectivity(void)
 		}
 		if (show_unreachable && !(obj->flags & REACHABLE)) {
-			if (obj->attached_deltas)
-				printf("foreign delta reference %s\n", 
-				       sha1_to_hex(obj->sha1));
-			else
-				printf("unreachable %s %s\n",
-				       obj->type, sha1_to_hex(obj->sha1));
+			printf("unreachable %s %s\n",
+			       obj->type, sha1_to_hex(obj->sha1));
 			continue;
 		}
@@ -240,8 +201,6 @@ static int fsck_sha1(unsigned char *sha1)
 		return fsck_commit((struct commit *) obj);
 	if (obj->type == tag_type)
 		return fsck_tag((struct tag *) obj);
-	if (!obj->type && obj->delta)
-		return 0;
 	return -1;
 }
@@ -427,10 +386,6 @@ int main(int argc, char **argv)
 			show_root = 1;
 			continue;
 		}
-		if (!strcmp(arg, "--delta-depth")) {
-			show_max_delta_depth = 1;
-			continue;
-		}
 		if (!strcmp(arg, "--cache")) {
 			keep_cache_objects = 1;
 			continue;
@@ -447,8 +402,6 @@ int main(int argc, char **argv)
 	}
 	fsck_sha1_list();
-	expand_deltas();
-
 	heads = 0;
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i]; 

git-deltafy-script

-#!/bin/bash
-
-# Example script to deltify an entire GIT repository based on the commit list.
-# The most recent version of a file is the reference and previous versions
-# are made delta against the best earlier version available. And so on for
-# successive versions going back in time.  This way the increasing delta
-# overhead is pushed towards older versions of any given file.
-#
-# The -d argument allows to provide a limit on the delta chain depth.
-# If 0 is passed then everything is undeltafied.  Limiting the delta
-# depth is meaningful for subsequent access performance to old revisions.
-# A value of 16 might be a good compromize between performance and good
-# space saving.  Current default is unbounded.
-#
-# The --max-behind=30 argument is passed to git-mkdelta so to keep
-# combinations and memory usage bounded a bit.  If you have lots of memory
-# and CPU power you may remove it (or set to 0) to let git-mkdelta find the
-# best delta match regardless of the number of revisions for a given file.
-# You can also make the value smaller to make it faster and less
-# memory hungry.  A value of 5 ought to still give pretty good results.
-# When set to 0 or ommitted then look behind is unbounded.  Note that
-# git-mkdelta might die with a segmentation fault in that case if it
-# runs out of memory.  Note that the GIT repository will still be consistent
-# even if git-mkdelta dies unexpectedly.
-
-set -e
-
-max_depth=
-[ "$1" == "-d" ] && max_depth="--max-depth=$2" && shift 2
-
-overlap=30
-max_behind="--max-behind=$overlap"
-
-function process_list() {
-	if [ "$list" ]; then
-		echo "Processing $curr_file"
-		echo "$list" | xargs git-mkdelta $max_depth $max_behind -v
-	fi
-}
-
-rev_list=""
-curr_file=""
-
-git-rev-list HEAD |
-while true; do
-	# Let's batch revisions into groups of 1000 to give it a chance to
-	# scale with repositories containing long revision lists.  We also
-	# overlap with the previous batch the size of mkdelta's look behind
-	# value in order to account for the processing discontinuity.
-	rev_list="$(echo -e -n "$rev_list" | tail --lines=$overlap)"
-	for i in $(seq 1000); do
-		read rev || break
-		rev_list="$rev_list$rev\n"
-	done
-	echo -e -n "$rev_list" |
-	git-diff-tree -r -t --stdin |
-	awk '/^:/ { if ($5 == "M") printf "%s %s\n%s %s\n", $4, $6, $3, $6 }' |
-	LC_ALL=C sort -s -k 2 | uniq |
-	while read sha1 file; do
-		if [ "$file" == "$curr_file" ]; then
-			list="$list $sha1"
-		else
-			process_list
-			curr_file="$file"
-			list="$sha1"
-		fi
-	done
-	[ "$rev" ] || break
-done
-process_list
-
-curr_file="root directory"
-list="$(
-	git-rev-list HEAD |
-	while read commit; do
-		git-cat-file commit $commit |
-		sed -n 's/tree //p;Q'
-	done
-	)"
-process_list
-

http-pull.c

@@ -150,10 +150,6 @@ int main(int argc, char **argv)
 			get_tree = 1;
 		} else if (argv[arg][1] == 'c') {
 			get_history = 1;
-		} else if (argv[arg][1] == 'd') {
-			get_delta = 0;
-		} else if (!strcmp(argv[arg], "--recover")) {
-			get_delta = 2;
 		} else if (argv[arg][1] == 'a') {
 			get_all = 1;
 			get_tree = 1;

local-pull.c

@@ -120,10 +120,6 @@ int main(int argc, char **argv)
 			get_tree = 1;
 		else if (argv[arg][1] == 'c')
 			get_history = 1;
-		else if (argv[arg][1] == 'd')
-			get_delta = 0;
-		else if (!strcmp(argv[arg], "--recover"))
-			get_delta = 2;
 		else if (argv[arg][1] == 'a') {
 			get_all = 1;
 			get_tree = 1;

mkdelta.c

-/*
- * Deltafication of a GIT database.
- *
- * (C) 2005 Nicolas Pitre <nico@cam.org>
- *
- * This code is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-
-#include "cache.h"
-#include "delta.h"
-
-static int replace_object(char *buf, unsigned long size, unsigned char *sha1)
-{
-	char tmpfile[PATH_MAX];
-	int fd;
-
-	snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
-	fd = mkstemp(tmpfile);
-	if (fd < 0)
-		return error("%s: %s\n", tmpfile, strerror(errno));
-	if (write(fd, buf, size) != size) {
-		perror("unable to write file");
-		close(fd);
-		unlink(tmpfile);
-		return -1;
-	}
-	fchmod(fd, 0444);
-	close(fd);
-	if (rename(tmpfile, sha1_file_name(sha1))) {
-		perror("unable to replace original object");
-		unlink(tmpfile);
-		return -1;
-	}
-	return 0;
-}
-
-static void *create_object(unsigned char *buf, unsigned long len,
-			   char *hdr, int hdrlen, unsigned long *retsize)
-{
-	unsigned char *compressed;
-	unsigned long size;
-	z_stream stream;
-
-	/* Set it up */
-	memset(&stream, 0, sizeof(stream));
-	deflateInit(&stream, Z_BEST_COMPRESSION);
-	size = deflateBound(&stream, len+hdrlen);
-	compressed = xmalloc(size);
-
-	/* Compress it */
-	stream.next_out = compressed;
-	stream.avail_out = size;
-
-	/* First header.. */
-	stream.next_in = (unsigned char *)hdr;
-	stream.avail_in = hdrlen;
-	while (deflate(&stream, 0) == Z_OK)
-		/* nothing */;
-
-	/* Then the data itself.. */
-	stream.next_in = buf;
-	stream.avail_in = len;
-	while (deflate(&stream, Z_FINISH) == Z_OK)
-		/* nothing */;
-	deflateEnd(&stream);
-	*retsize = stream.total_out;
-	return compressed;
-}
-
-static int restore_original_object(unsigned char *buf, unsigned long len,
-				   char *type, unsigned char *sha1)
-{
-	char hdr[50];
-	int hdrlen, ret;
-	void *compressed;
-	unsigned long size;
-
-	hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
-	compressed = create_object(buf, len, hdr, hdrlen, &size);
-	ret = replace_object(compressed, size, sha1);
-	free(compressed);
-	return ret;
-}
-
-static void *create_delta_object(unsigned char *buf, unsigned long len,
-				 unsigned char *sha1_ref, unsigned long *size)
-{
-	char hdr[50];
-	int hdrlen;
-
-	/* Generate the header + sha1 of reference for delta */
-	hdrlen = sprintf(hdr, "delta %lu", len+20)+1;
-	memcpy(hdr + hdrlen, sha1_ref, 20);
-	hdrlen += 20;
-
-	return create_object(buf, len, hdr, hdrlen, size);
-}
-
-static void *get_buffer(unsigned char *sha1, char *type,
-			unsigned long *size, unsigned long *compsize)
-{
-	unsigned long mapsize;
-	void *map = map_sha1_file(sha1, &mapsize);
-	if (map) {
-		void *buffer = unpack_sha1_file(map, mapsize, type, size);
-		munmap(map, mapsize);
-		if (compsize)
-			*compsize = mapsize;
-		if (buffer)
-			return buffer;
-	}
-	error("unable to get object %s", sha1_to_hex(sha1));
-	return NULL;
-}
-
-static void *expand_delta(void *delta, unsigned long *size, char *type,
-			  unsigned int *depth, unsigned char **links)
-{
-	void *buf = NULL;
-	unsigned int level = (*depth)++;
-	if (*size < 20) {
-		error("delta object is bad");
-		free(delta);
-	} else {
-		unsigned long ref_size;
-		void *ref = get_buffer(delta, type, &ref_size, NULL);
-		if (ref && !strcmp(type, "delta"))
-			ref = expand_delta(ref, &ref_size, type, depth, links);
-		else if (ref)
-{
-			*links = xmalloc(*depth * 20);
-}
-		if (ref) {
-			buf = patch_delta(ref, ref_size, delta+20, *size-20, size);
-			free(ref);
-			if (buf)
-				memcpy(*links + level*20, delta, 20);
-			else
-				free(*links);
-		}
-		free(delta);
-	}
-	return buf;
-}
-
-static char *mkdelta_usage =
-"mkdelta [--max-depth=N] [--max-behind=N] <reference_sha1> <target_sha1> [<next_sha1> ...]";
-
-struct delta {
-	unsigned char sha1[20];		/* object sha1 */
-	unsigned long size;		/* object size */
-	void *buf;			/* object content */
-	unsigned char *links;		/* delta reference links */
-	unsigned int depth;		/* delta depth */
-};
-	
-int main(int argc, char **argv)
-{
-	struct delta *ref, trg;
-	char ref_type[20], trg_type[20], *skip_reason;
-	void *best_buf;
-	unsigned long best_size, orig_size, orig_compsize;
-	unsigned int r, orig_ref, best_ref, nb_refs, next_ref, max_refs = 0;
-	unsigned int i, duplicate, skip_lvl, verbose = 0, quiet = 0;
-	unsigned int max_depth = -1;
-
-	for (i = 1; i < argc; i++) {
-		if (!strcmp(argv[i], "-v")) {
-			verbose = 1;
-			quiet = 0;
-		} else if (!strcmp(argv[i], "-q")) {
-			quiet = 1;
-			verbose = 0;
-		} else if (!strcmp(argv[i], "-d") && i+1 < argc) {
-			max_depth = atoi(argv[++i]);
-		} else if (!strncmp(argv[i], "--max-depth=", 12)) {
-			max_depth = atoi(argv[i]+12);
-		} else if (!strcmp(argv[i], "-b") && i+1 < argc) {
-			max_refs = atoi(argv[++i]);
-		} else if (!strncmp(argv[i], "--max-behind=", 13)) {
-			max_refs = atoi(argv[i]+13);
-		} else
-			break;
-	}
-
-	if (i + (max_depth != 0) >= argc)
-		usage(mkdelta_usage);
-
-	if (!max_refs || max_refs > argc - i)
-		max_refs = argc - i;
-	ref = xmalloc(max_refs * sizeof(*ref));
-	for (r = 0; r < max_refs; r++)
-		ref[r].buf = ref[r].links = NULL;
-	next_ref = nb_refs = 0;
-
-	do {
-		if (get_sha1(argv[i], trg.sha1))
-			die("bad sha1 %s", argv[i]);
-		trg.buf = get_buffer(trg.sha1, trg_type, &trg.size, &orig_compsize);
-		if (trg.buf && !trg.size) {
-			if (verbose)
-				printf("skip    %s (object is empty)\n", argv[i]);
-			continue;
-		}
-		orig_size = trg.size;
-		orig_ref = -1;
-		trg.depth = 0;
-		trg.links = NULL;
-		if (trg.buf && !strcmp(trg_type, "delta")) {
-			for (r = 0; r < nb_refs; r++)
-				if (!memcmp(trg.buf, ref[r].sha1, 20))
-					break;
-			if (r < nb_refs) {
-				/* no need to reload the reference object */
-				trg.depth = ref[r].depth + 1;
-				trg.links = xmalloc(trg.depth*20);
-				memcpy(trg.links, trg.buf, 20);
-				memcpy(trg.links+20, ref[r].links, ref[r].depth*20);
-				trg.buf = patch_delta(ref[r].buf, ref[r].size,
-						      trg.buf+20, trg.size-20,
-						      &trg.size);
-				strcpy(trg_type, ref_type);
-				orig_ref = r;
-			} else {
-				trg.buf = expand_delta(trg.buf, &trg.size, trg_type,
-						       &trg.depth, &trg.links);
-			}
-		}
-		if (!trg.buf)
-			die("unable to read target object %s", argv[i]);
-
-		if (!nb_refs) {
-			strcpy(ref_type, trg_type);
-		} else if (max_depth && strcmp(ref_type, trg_type)) {
-			die("type mismatch for object %s", argv[i]);
-		}
-
-		duplicate = 0;
-		best_buf = NULL;
-		best_size = -1;
-		best_ref = -1;
-		skip_lvl = 0;
-		skip_reason = NULL;
-		for (r = 0; max_depth && r < nb_refs; r++) {
-			void *delta_buf, *comp_buf;
-			unsigned long delta_size, comp_size;
-			unsigned int l;
-
-			duplicate = !memcmp(trg.sha1, ref[r].sha1, 20);
-			if (duplicate) {
-				skip_reason = "already seen";
-				break;
-			}
-			if (ref[r].depth >= max_depth) {
-				if (skip_lvl < 1) {
-					skip_reason = "exceeding max link depth";
-					skip_lvl = 1;
-				}
-				continue;
-			}
-			for (l = 0; l < ref[r].depth; l++)
-				if (!memcmp(trg.sha1, ref[r].links + l*20, 20))
-					break;
-			if (l != ref[r].depth) {
-				if (skip_lvl < 2) {
-					skip_reason = "would create a loop";
-					skip_lvl = 2;
-				}
-				continue;
-			}
-			if (trg.depth < max_depth && r == orig_ref) {
-				if (skip_lvl < 3) {
-					skip_reason = "delta already in place";
-					skip_lvl = 3;
-				}
-				continue;
-			}
-			delta_buf = diff_delta(ref[r].buf, ref[r].size,
-					       trg.buf, trg.size,
-					       &delta_size, ~0UL);
-			if (!delta_buf)
-				die("out of memory");
-			if (trg.depth < max_depth &&
-			    delta_size+20 >= orig_size) {
-				/* no need to even try to compress if original
-				   object is smaller than this delta */
-				free(delta_buf);
-				if (skip_lvl < 4) {
-					skip_reason = "no size reduction";
-					skip_lvl = 4;
-				}
-				continue;
-			}
-			comp_buf = create_delta_object(delta_buf, delta_size,
-						       ref[r].sha1, &comp_size);
-			if (!comp_buf)
-				die("out of memory");
-			free(delta_buf);
-			if (trg.depth < max_depth &&
-			    comp_size >= orig_compsize) {
-				free(comp_buf);
-				if (skip_lvl < 5) {
-					skip_reason = "no size reduction";
-					skip_lvl = 5;
-				}
-				continue;
-			}
-			if ((comp_size < best_size) ||
-			    (comp_size == best_size &&
-			     ref[r].depth < ref[best_ref].depth)) {
-				free(best_buf);
-				best_buf = comp_buf;
-				best_size = comp_size;
-				best_ref = r;
-			}
-		}
-
-		if (best_buf) {
-			if (replace_object(best_buf, best_size, trg.sha1))
-				die("unable to write delta for %s", argv[i]);
-			free(best_buf);
-			free(trg.links);
-			trg.depth = ref[best_ref].depth + 1;
-			trg.links = xmalloc(trg.depth*20);
-			memcpy(trg.links, ref[best_ref].sha1, 20);
-			memcpy(trg.links+20, ref[best_ref].links, ref[best_ref].depth*20);
-			if (!quiet)
-				printf("delta   %s (size=%ld.%02ld%% depth=%d dist=%d)\n",
-				       argv[i], best_size*100 / orig_compsize,
-				       (best_size*10000 / orig_compsize)%100,
-				       trg.depth,
-				       (next_ref - best_ref + max_refs)
-				       % (max_refs + 1) + 1);
-		} else if (trg.depth > max_depth) {
-			if (restore_original_object(trg.buf, trg.size, trg_type, trg.sha1))
-				die("unable to restore %s", argv[i]);
-			if (!quiet)
-				printf("undelta %s (depth was %d)\n",
-				       argv[i], trg.depth);
-			trg.depth = 0;
-			free(trg.links);
-			trg.links = NULL;
-		} else if (skip_reason && verbose) {
-			printf("skip    %s (%s)\n", argv[i], skip_reason);
-		}
-
-		if (!duplicate) {
-			free(ref[next_ref].buf);
-			free(ref[next_ref].links);
-			ref[next_ref] = trg;
-			if (++next_ref > nb_refs)
-				nb_refs = next_ref;
-			if (next_ref == max_refs)
-				next_ref = 0;
-		} else {
-			free(trg.buf);
-			free(trg.links);
-		}
-	} while (++i < argc);
-
-	return 0;
-}

object.c

@@ -4,7 +4,6 @@
 #include "commit.h"
 #include "cache.h"
 #include "tag.h"
-#include "delta.h"
 struct object **objs;
 int nr_objs;
@@ -116,25 +115,14 @@ struct object *lookup_object_type(const unsigned char *sha1, const char *type)
 struct object *parse_object(const unsigned char *sha1)
 {
-	unsigned long mapsize;
-	void *map = map_sha1_file(sha1, &mapsize);
-	if (map) {
-		int is_delta;
+	unsigned long size;
+	char type[20];
+	void *buffer = read_sha1_file(sha1, type, &size);
+	if (buffer) {
 		struct object *obj;
-		char type[100];
-		unsigned long size;
-		void *buffer = unpack_sha1_file(map, mapsize, type, &size);
-		munmap(map, mapsize);
-		if (!buffer)
-			return NULL;
-		is_delta = !strcmp(type, "delta");
-		if (!is_delta && check_sha1_signature(sha1, buffer, size, type) < 0)
+		if (check_sha1_signature(sha1, buffer, size, type) < 0)
 			printf("sha1 mismatch %s\n", sha1_to_hex(sha1));
-		if (is_delta) {
-			struct delta *delta = lookup_delta(sha1);
-			parse_delta_buffer(delta, buffer, size);
-			obj = (struct object *) delta;
-		} else if (!strcmp(type, "blob")) {
+		if (!strcmp(type, "blob")) {
 			struct blob *blob = lookup_blob(sha1);
 			parse_blob_buffer(blob, buffer, size);
 			obj = &blob->object;

object.h

@@ -10,12 +10,10 @@ struct object_list {
 struct object {
 	unsigned parsed : 1;
 	unsigned used : 1;
-	unsigned delta : 1;
 	unsigned int flags;
 	unsigned char sha1[20];
 	const char *type;
 	struct object_list *refs;
-	struct object_list *attached_deltas;
 	void *util;
 };

pack-objects.c

@@ -11,7 +11,7 @@ enum object_type {
 	OBJ_COMMIT,
 	OBJ_TREE,
 	OBJ_BLOB,
-	OBJ_DELTA	// NOTE! This is _not_ the same as a "delta" object in the filesystem
+	OBJ_DELTA
 };
 struct object_entry {