Merge branch 'cc/replace'

* cc/replace:
  t6050: check pushing something based on a replaced commit
  Documentation: add documentation for "git replace"
  Add git-replace to .gitignore
  builtin-replace: use "usage_msg_opt" to give better error messages
  parse-options: add new function "usage_msg_opt"
  builtin-replace: teach "git replace" to actually replace
  Add new "git replace" command
  environment: add global variable to disable replacement
  mktag: call "check_sha1_signature" with the replacement sha1
  replace_object: add a test case
  object: call "check_sha1_signature" with the replacement sha1
  sha1_file: add a "read_sha1_file_repl" function
  replace_object: add mechanism to replace objects found in "refs/replace/"
  refs: add a "for_each_replace_ref" function

.gitignore

@@ -105,6 +105,7 @@ git-reflog
 git-relink
 git-remote
 git-repack
+git-replace
 git-repo-config
 git-request-pull
 git-rerere

Documentation/git-replace.txt

@@ -0,0 +1,71 @@
+git-replace(1)
+==============
+
+NAME
+----
+git-replace - Create, list, delete refs to replace objects
+
+SYNOPSIS
+--------
+[verse]
+'git replace' [-f] <object> <replacement>
+'git replace' -d <object>...
+'git replace' -l [<pattern>]
+
+DESCRIPTION
+-----------
+Adds a 'replace' reference in `.git/refs/replace/`
+
+The name of the 'replace' reference is the SHA1 of the object that is
+replaced. The content of the replace reference is the SHA1 of the
+replacement object.
+
+Unless `-f` is given, the replace reference must not yet exist in
+`.git/refs/replace/` directory.
+
+OPTIONS
+-------
+-f::
+	If an existing replace ref for the same object exists, it will
+	be overwritten (instead of failing).
+
+-d::
+	Delete existing replace refs for the given objects.
+
+-l <pattern>::
+	List replace refs for objects that match the given pattern (or
+	all if no pattern is given).
+	Typing "git replace" without arguments, also lists all replace
+	refs.
+
+BUGS
+----
+Comparing blobs or trees that have been replaced with those that
+replace them will not work properly. And using 'git reset --hard' to
+go back to a replaced commit will move the branch to the replacement
+commit instead of the replaced commit.
+
+There may be other problems when using 'git rev-list' related to
+pending objects. And of course things may break if an object of one
+type is replaced by an object of another type (for example a blob
+replaced by a commit).
+
+SEE ALSO
+--------
+linkgit:git-tag[1]
+linkgit:git-branch[1]
+
+Author
+------
+Written by Christian Couder <chriscool@tuxfamily.org> and Junio C
+Hamano <gitster@pobox.com>, based on 'git tag' by Kristian Hogsberg
+<krh@redhat.com> and Carlos Rica <jasampler@gmail.com>.
+
+Documentation
+--------------
+Documentation by Christian Couder <chriscool@tuxfamily.org> and the
+git-list <git@vger.kernel.org>, based on 'git tag' documentation.
+
+GIT
+---
+Part of the linkgit:git[1] suite

Makefile

@@ -536,6 +536,7 @@ LIB_OBJS += read-cache.o
 LIB_OBJS += reflog-walk.o
 LIB_OBJS += refs.o
 LIB_OBJS += remote.o
+LIB_OBJS += replace_object.o
 LIB_OBJS += rerere.o
 LIB_OBJS += revision.o
 LIB_OBJS += run-command.o
@@ -625,6 +626,7 @@ BUILTIN_OBJS += builtin-read-tree.o
 BUILTIN_OBJS += builtin-receive-pack.o
 BUILTIN_OBJS += builtin-reflog.o
 BUILTIN_OBJS += builtin-remote.o
+BUILTIN_OBJS += builtin-replace.o
 BUILTIN_OBJS += builtin-rerere.o
 BUILTIN_OBJS += builtin-reset.o
 BUILTIN_OBJS += builtin-rev-list.o

builtin-fsck.c

@@ -589,6 +589,7 @@ int cmd_fsck(int argc, const char **argv, const char *prefix)
 	struct alternate_object_database *alt;
 
 	errors_found = 0;
+	read_replace_refs = 0;
 
 	argc = parse_options(argc, argv, prefix, fsck_opts, fsck_usage, 0);
 	if (write_lost_and_found) {

builtin-pack-objects.c

@@ -2098,6 +2098,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 	int rp_ac_alloc = 64;
 	int rp_ac;
 
+	read_replace_refs = 0;
+
 	rp_av = xcalloc(rp_ac_alloc, sizeof(*rp_av));
 
 	rp_av[0] = "pack-objects";

builtin-prune.c

@@ -140,6 +140,7 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
 	char *s;
 
 	save_commit_buffer = 0;
+	read_replace_refs = 0;
 	init_revisions(&revs, prefix);
 
 	argc = parse_options(argc, argv, prefix, options, prune_usage, 0);

builtin-replace.c

@@ -0,0 +1,159 @@
+/*
+ * Builtin "git replace"
+ *
+ * Copyright (c) 2008 Christian Couder <chriscool@tuxfamily.org>
+ *
+ * Based on builtin-tag.c by Kristian Høgsberg <krh@redhat.com>
+ * and Carlos Rica <jasampler@gmail.com> that was itself based on
+ * git-tag.sh and mktag.c by Linus Torvalds.
+ */
+
+#include "cache.h"
+#include "builtin.h"
+#include "refs.h"
+#include "parse-options.h"
+
+static const char * const git_replace_usage[] = {
+	"git replace [-f] <object> <replacement>",
+	"git replace -d <object>...",
+	"git replace -l [<pattern>]",
+	NULL
+};
+
+static int show_reference(const char *refname, const unsigned char *sha1,
+			  int flag, void *cb_data)
+{
+	const char *pattern = cb_data;
+
+	if (!fnmatch(pattern, refname, 0))
+		printf("%s\n", refname);
+
+	return 0;
+}
+
+static int list_replace_refs(const char *pattern)
+{
+	if (pattern == NULL)
+		pattern = "*";
+
+	for_each_replace_ref(show_reference, (void *) pattern);
+
+	return 0;
+}
+
+typedef int (*each_replace_name_fn)(const char *name, const char *ref,
+				    const unsigned char *sha1);
+
+static int for_each_replace_name(const char **argv, each_replace_name_fn fn)
+{
+	const char **p;
+	char ref[PATH_MAX];
+	int had_error = 0;
+	unsigned char sha1[20];
+
+	for (p = argv; *p; p++) {
+		if (snprintf(ref, sizeof(ref), "refs/replace/%s", *p)
+					>= sizeof(ref)) {
+			error("replace ref name too long: %.*s...", 50, *p);
+			had_error = 1;
+			continue;
+		}
+		if (!resolve_ref(ref, sha1, 1, NULL)) {
+			error("replace ref '%s' not found.", *p);
+			had_error = 1;
+			continue;
+		}
+		if (fn(*p, ref, sha1))
+			had_error = 1;
+	}
+	return had_error;
+}
+
+static int delete_replace_ref(const char *name, const char *ref,
+			      const unsigned char *sha1)
+{
+	if (delete_ref(ref, sha1, 0))
+		return 1;
+	printf("Deleted replace ref '%s'\n", name);
+	return 0;
+}
+
+static int replace_object(const char *object_ref, const char *replace_ref,
+			  int force)
+{
+	unsigned char object[20], prev[20], repl[20];
+	char ref[PATH_MAX];
+	struct ref_lock *lock;
+
+	if (get_sha1(object_ref, object))
+		die("Failed to resolve '%s' as a valid ref.", object_ref);
+	if (get_sha1(replace_ref, repl))
+		die("Failed to resolve '%s' as a valid ref.", replace_ref);
+
+	if (snprintf(ref, sizeof(ref),
+		     "refs/replace/%s",
+		     sha1_to_hex(object)) > sizeof(ref) - 1)
+		die("replace ref name too long: %.*s...", 50, ref);
+	if (check_ref_format(ref))
+		die("'%s' is not a valid ref name.", ref);
+
+	if (!resolve_ref(ref, prev, 1, NULL))
+		hashclr(prev);
+	else if (!force)
+		die("replace ref '%s' already exists", ref);
+
+	lock = lock_any_ref_for_update(ref, prev, 0);
+	if (!lock)
+		die("%s: cannot lock the ref", ref);
+	if (write_ref_sha1(lock, repl, NULL) < 0)
+		die("%s: cannot update the ref", ref);
+
+	return 0;
+}
+
+int cmd_replace(int argc, const char **argv, const char *prefix)
+{
+	int list = 0, delete = 0, force = 0;
+	struct option options[] = {
+		OPT_BOOLEAN('l', NULL, &list, "list replace refs"),
+		OPT_BOOLEAN('d', NULL, &delete, "delete replace refs"),
+		OPT_BOOLEAN('f', NULL, &force, "replace the ref if it exists"),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options, git_replace_usage, 0);
+
+	if (list && delete)
+		usage_msg_opt("-l and -d cannot be used together",
+			      git_replace_usage, options);
+
+	if (force && (list || delete))
+		usage_msg_opt("-f cannot be used with -d or -l",
+			      git_replace_usage, options);
+
+	/* Delete refs */
+	if (delete) {
+		if (argc < 1)
+			usage_msg_opt("-d needs at least one argument",
+				      git_replace_usage, options);
+		return for_each_replace_name(argv, delete_replace_ref);
+	}
+
+	/* Replace object */
+	if (!list && argc) {
+		if (argc != 2)
+			usage_msg_opt("bad number of arguments",
+				      git_replace_usage, options);
+		return replace_object(argv[0], argv[1], force);
+	}
+
+	/* List refs, even if "list" is not set */
+	if (argc > 1)
+		usage_msg_opt("only one pattern can be given with -l",
+			      git_replace_usage, options);
+	if (force)
+		usage_msg_opt("-f needs some arguments",
+			      git_replace_usage, options);
+
+	return list_replace_refs(argv[0]);
+}

builtin-unpack-objects.c

@@ -495,6 +495,8 @@ int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
 	int i;
 	unsigned char sha1[20];
 
+	read_replace_refs = 0;
+
 	git_config(git_default_config, NULL);
 
 	quiet = !isatty(2);

builtin.h

@@ -111,5 +111,6 @@ extern int cmd_write_tree(int argc, const char **argv, const char *prefix);
 extern int cmd_verify_pack(int argc, const char **argv, const char *prefix);
 extern int cmd_show_ref(int argc, const char **argv, const char *prefix);
 extern int cmd_pack_refs(int argc, const char **argv, const char *prefix);
+extern int cmd_replace(int argc, const char **argv, const char *prefix);
 
 #endif

cache.h

@@ -520,6 +520,7 @@ extern size_t packed_git_window_size;
 extern size_t packed_git_limit;
 extern size_t delta_base_cache_limit;
 extern int auto_crlf;
+extern int read_replace_refs;
 extern int fsync_object_files;
 extern int core_preload_index;
 
@@ -656,7 +657,11 @@ char *strip_path_suffix(const char *path, const char *suffix);
 
 /* Read and unpack a sha1 file into memory, write memory to a sha1 file */
 extern int sha1_object_info(const unsigned char *, unsigned long *);
-extern void * read_sha1_file(const unsigned char *sha1, enum object_type *type, unsigned long *size);
+extern void *read_sha1_file_repl(const unsigned char *sha1, enum object_type *type, unsigned long *size, const unsigned char **replacement);
+static inline void *read_sha1_file(const unsigned char *sha1, enum object_type *type, unsigned long *size)
+{
+	return read_sha1_file_repl(sha1, type, size, NULL);
+}
 extern int hash_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *sha1);
 extern int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *return_sha1);
 extern int pretend_sha1_file(void *, unsigned long, enum object_type, unsigned char *);

commit.h

@@ -123,6 +123,8 @@ struct commit_graft *read_graft_line(char *buf, int len);
 int register_commit_graft(struct commit_graft *, int);
 struct commit_graft *lookup_commit_graft(const unsigned char *sha1);
 
+const unsigned char *lookup_replace_object(const unsigned char *sha1);
+
 extern struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2, int cleanup);
 extern struct commit_list *get_merge_bases_many(struct commit *one, int n, struct commit **twos, int cleanup);
 extern struct commit_list *get_octopus_merge_bases(struct commit_list *in);

environment.c

@@ -39,6 +39,7 @@ int pager_use_color = 1;
 const char *editor_program;
 const char *excludes_file;
 int auto_crlf = 0;	/* 1: both ways, -1: only when adding git objects */
+int read_replace_refs = 1;
 enum safe_crlf safe_crlf = SAFE_CRLF_WARN;
 unsigned whitespace_rule_cfg = WS_DEFAULT_RULE;
 enum branch_track git_branch_track = BRANCH_TRACK_REMOTE;

git.c

@@ -339,6 +339,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "receive-pack", cmd_receive_pack },
 		{ "reflog", cmd_reflog, RUN_SETUP },
 		{ "remote", cmd_remote, RUN_SETUP },
+		{ "replace", cmd_replace, RUN_SETUP },
 		{ "repo-config", cmd_config },
 		{ "rerere", cmd_rerere, RUN_SETUP },
 		{ "reset", cmd_reset, RUN_SETUP },

mktag.c

@@ -19,16 +19,17 @@
 /*
  * We refuse to tag something we can't verify. Just because.
  */
-static int verify_object(unsigned char *sha1, const char *expected_type)
+static int verify_object(const unsigned char *sha1, const char *expected_type)
 {
 	int ret = -1;
 	enum object_type type;
 	unsigned long size;
-	void *buffer = read_sha1_file(sha1, &type, &size);
+	const unsigned char *repl;
+	void *buffer = read_sha1_file_repl(sha1, &type, &size, &repl);
 
 	if (buffer) {
 		if (type == type_from_string(expected_type))
-			ret = check_sha1_signature(sha1, buffer, size, expected_type);
+			ret = check_sha1_signature(repl, buffer, size, expected_type);
 		free(buffer);
 	}
 	return ret;

object.c

@@ -188,17 +188,18 @@ struct object *parse_object(const unsigned char *sha1)
 	unsigned long size;
 	enum object_type type;
 	int eaten;
-	void *buffer = read_sha1_file(sha1, &type, &size);
+	const unsigned char *repl;
+	void *buffer = read_sha1_file_repl(sha1, &type, &size, &repl);
 
 	if (buffer) {
 		struct object *obj;
-		if (check_sha1_signature(sha1, buffer, size, typename(type)) < 0) {
+		if (check_sha1_signature(repl, buffer, size, typename(type)) < 0) {
 			free(buffer);
-			error("sha1 mismatch %s\n", sha1_to_hex(sha1));
+			error("sha1 mismatch %s\n", sha1_to_hex(repl));
 			return NULL;
 		}
 
-		obj = parse_object_buffer(sha1, type, size, buffer, &eaten);
+		obj = parse_object_buffer(repl, type, size, buffer, &eaten);
 		if (!eaten)
 			free(buffer);
 		return obj;

parse-options.c

@@ -549,6 +549,14 @@ void usage_with_options(const char * const *usagestr,
 	exit(129);
 }
 
+void usage_msg_opt(const char *msg,
+		   const char * const *usagestr,
+		   const struct option *options)
+{
+	fprintf(stderr, "%s\n\n", msg);
+	usage_with_options(usagestr, options);
+}
+
 int parse_options_usage(const char * const *usagestr,
 			const struct option *opts)
 {

parse-options.h

@@ -145,6 +145,10 @@ extern int parse_options(int argc, const char **argv, const char *prefix,
 extern NORETURN void usage_with_options(const char * const *usagestr,
                                         const struct option *options);
 
+extern NORETURN void usage_msg_opt(const char *msg,
+				   const char * const *usagestr,
+				   const struct option *options);
+
 /*----- incremental advanced APIs -----*/
 
 enum {

refs.c

@@ -668,6 +668,11 @@ int for_each_remote_ref(each_ref_fn fn, void *cb_data)
 	return for_each_ref_in("refs/remotes/", fn, cb_data);
 }
 
+int for_each_replace_ref(each_ref_fn fn, void *cb_data)
+{
+	return do_for_each_ref("refs/replace/", fn, 13, 0, cb_data);
+}
+
 int for_each_rawref(each_ref_fn fn, void *cb_data)
 {
 	return do_for_each_ref("refs/", fn, 0,

refs.h

@@ -24,6 +24,7 @@ extern int for_each_ref_in(const char *, each_ref_fn, void *);
 extern int for_each_tag_ref(each_ref_fn, void *);
 extern int for_each_branch_ref(each_ref_fn, void *);
 extern int for_each_remote_ref(each_ref_fn, void *);
+extern int for_each_replace_ref(each_ref_fn, void *);
 
 /* can be used to learn about broken ref and symref */
 extern int for_each_rawref(each_ref_fn, void *);

replace_object.c

@@ -0,0 +1,114 @@
+#include "cache.h"
+#include "sha1-lookup.h"
+#include "refs.h"
+
+static struct replace_object {
+	unsigned char sha1[2][20];
+} **replace_object;
+
+static int replace_object_alloc, replace_object_nr;
+
+static const unsigned char *replace_sha1_access(size_t index, void *table)
+{
+	struct replace_object **replace = table;
+	return replace[index]->sha1[0];
+}
+
+static int replace_object_pos(const unsigned char *sha1)
+{
+	return sha1_pos(sha1, replace_object, replace_object_nr,
+			replace_sha1_access);
+}
+
+static int register_replace_object(struct replace_object *replace,
+				   int ignore_dups)
+{
+	int pos = replace_object_pos(replace->sha1[0]);
+
+	if (0 <= pos) {
+		if (ignore_dups)
+			free(replace);
+		else {
+			free(replace_object[pos]);
+			replace_object[pos] = replace;
+		}
+		return 1;
+	}
+	pos = -pos - 1;
+	if (replace_object_alloc <= ++replace_object_nr) {
+		replace_object_alloc = alloc_nr(replace_object_alloc);
+		replace_object = xrealloc(replace_object,
+					  sizeof(*replace_object) *
+					  replace_object_alloc);
+	}
+	if (pos < replace_object_nr)
+		memmove(replace_object + pos + 1,
+			replace_object + pos,
+			(replace_object_nr - pos - 1) *
+			sizeof(*replace_object));
+	replace_object[pos] = replace;
+	return 0;
+}
+
+static int register_replace_ref(const char *refname,
+				const unsigned char *sha1,
+				int flag, void *cb_data)
+{
+	/* Get sha1 from refname */
+	const char *slash = strrchr(refname, '/');
+	const char *hash = slash ? slash + 1 : refname;
+	struct replace_object *repl_obj = xmalloc(sizeof(*repl_obj));
+
+	if (strlen(hash) != 40 || get_sha1_hex(hash, repl_obj->sha1[0])) {
+		free(repl_obj);
+		warning("bad replace ref name: %s", refname);
+		return 0;
+	}
+
+	/* Copy sha1 from the read ref */
+	hashcpy(repl_obj->sha1[1], sha1);
+
+	/* Register new object */
+	if (register_replace_object(repl_obj, 1))
+		die("duplicate replace ref: %s", refname);
+
+	return 0;
+}
+
+static void prepare_replace_object(void)
+{
+	static int replace_object_prepared;
+
+	if (replace_object_prepared)
+		return;
+
+	for_each_replace_ref(register_replace_ref, NULL);
+	replace_object_prepared = 1;
+}
+
+/* We allow "recursive" replacement. Only within reason, though */
+#define MAXREPLACEDEPTH 5
+
+const unsigned char *lookup_replace_object(const unsigned char *sha1)
+{
+	int pos, depth = MAXREPLACEDEPTH;
+	const unsigned char *cur = sha1;
+
+	if (!read_replace_refs)
+		return sha1;
+
+	prepare_replace_object();
+
+	/* Try to recursively replace the object */
+	do {
+		if (--depth < 0)
+			die("replace depth too high for object %s",
+			    sha1_to_hex(sha1));
+
+		pos = replace_object_pos(cur);
+		if (0 <= pos)
+			cur = replace_object[pos]->sha1[1];
+	} while (0 <= pos);
+
+	return cur;
+}

sha1_file.c

@@ -2144,13 +2144,26 @@ static void *read_object(const unsigned char *sha1, enum object_type *type,
 	return read_packed_sha1(sha1, type, size);
 }
 
-void *read_sha1_file(const unsigned char *sha1, enum object_type *type,
-		     unsigned long *size)
+void *read_sha1_file_repl(const unsigned char *sha1,
+			  enum object_type *type,
+			  unsigned long *size,
+			  const unsigned char **replacement)
 {
-	void *data = read_object(sha1, type, size);
+	const unsigned char *repl = lookup_replace_object(sha1);
+	void *data = read_object(repl, type, size);
+
+	/* die if we replaced an object with one that does not exist */
+	if (!data && repl != sha1)
+		die("replacement %s not found for %s",
+		    sha1_to_hex(repl), sha1_to_hex(sha1));
+
 	/* legacy behavior is to die on corrupted objects */
-	if (!data && (has_loose_object(sha1) || has_packed_and_bad(sha1)))
-		die("object %s is corrupted", sha1_to_hex(sha1));
+	if (!data && (has_loose_object(repl) || has_packed_and_bad(repl)))
+		die("object %s is corrupted", sha1_to_hex(repl));
+
+	if (replacement)
+		*replacement = repl;
+
 	return data;
 }
 

t/t6050-replace.sh

@@ -0,0 +1,200 @@
+#!/bin/sh
+#
+# Copyright (c) 2008 Christian Couder
+#
+test_description='Tests replace refs functionality'
+
+exec </dev/null
+
+. ./test-lib.sh
+
+add_and_commit_file()
+{
+    _file="$1"
+    _msg="$2"
+
+    git add $_file || return $?
+    test_tick || return $?
+    git commit --quiet -m "$_file: $_msg"
+}
+
+HASH1=
+HASH2=
+HASH3=
+HASH4=
+HASH5=
+HASH6=
+HASH7=
+
+test_expect_success 'set up buggy branch' '
+     echo "line 1" >> hello &&
+     echo "line 2" >> hello &&
+     echo "line 3" >> hello &&
+     echo "line 4" >> hello &&
+     add_and_commit_file hello "4 lines" &&
+     HASH1=$(git rev-parse --verify HEAD) &&
+     echo "line BUG" >> hello &&
+     echo "line 6" >> hello &&
+     echo "line 7" >> hello &&
+     echo "line 8" >> hello &&
+     add_and_commit_file hello "4 more lines with a BUG" &&
+     HASH2=$(git rev-parse --verify HEAD) &&
+     echo "line 9" >> hello &&
+     echo "line 10" >> hello &&
+     add_and_commit_file hello "2 more lines" &&
+     HASH3=$(git rev-parse --verify HEAD) &&
+     echo "line 11" >> hello &&
+     add_and_commit_file hello "1 more line" &&
+     HASH4=$(git rev-parse --verify HEAD) &&
+     sed -e "s/BUG/5/" hello > hello.new &&
+     mv hello.new hello &&
+     add_and_commit_file hello "BUG fixed" &&
+     HASH5=$(git rev-parse --verify HEAD) &&
+     echo "line 12" >> hello &&
+     echo "line 13" >> hello &&
+     add_and_commit_file hello "2 more lines" &&
+     HASH6=$(git rev-parse --verify HEAD)
+     echo "line 14" >> hello &&
+     echo "line 15" >> hello &&
+     echo "line 16" >> hello &&
+     add_and_commit_file hello "again 3 more lines" &&
+     HASH7=$(git rev-parse --verify HEAD)
+'
+
+test_expect_success 'replace the author' '
+     git cat-file commit $HASH2 | grep "author A U Thor" &&
+     R=$(git cat-file commit $HASH2 | sed -e "s/A U/O/" | git hash-object -t commit --stdin -w) &&
+     git cat-file commit $R | grep "author O Thor" &&
+     git update-ref refs/replace/$HASH2 $R &&
+     git show HEAD~5 | grep "O Thor" &&
+     git show $HASH2 | grep "O Thor"
+'
+
+cat >tag.sig <<EOF
+object $HASH2
+type commit
+tag mytag
+tagger T A Gger <> 0 +0000
+
+EOF
+
+test_expect_success 'tag replaced commit' '
+     git mktag <tag.sig >.git/refs/tags/mytag 2>message
+'
+
+test_expect_success '"git fsck" works' '
+     git fsck master > fsck_master.out &&
+     grep "dangling commit $R" fsck_master.out &&
+     grep "dangling tag $(cat .git/refs/tags/mytag)" fsck_master.out &&
+     test -z "$(git fsck)"
+'
+
+test_expect_success 'repack, clone and fetch work' '
+     git repack -a -d &&
+     git clone --no-hardlinks . clone_dir &&
+     cd clone_dir &&
+     git show HEAD~5 | grep "A U Thor" &&
+     git show $HASH2 | grep "A U Thor" &&
+     git cat-file commit $R &&
+     git repack -a -d &&
+     test_must_fail git cat-file commit $R &&
+     git fetch ../ "refs/replace/*:refs/replace/*" &&
+     git show HEAD~5 | grep "O Thor" &&
+     git show $HASH2 | grep "O Thor" &&
+     git cat-file commit $R &&
+     cd ..
+'
+
+test_expect_success '"git replace" listing and deleting' '
+     test "$HASH2" = "$(git replace -l)" &&
+     test "$HASH2" = "$(git replace)" &&
+     aa=${HASH2%??????????????????????????????????????} &&
+     test "$HASH2" = "$(git replace -l "$aa*")" &&
+     test_must_fail git replace -d $R &&
+     test_must_fail git replace -d &&
+     test_must_fail git replace -l -d $HASH2 &&
+     git replace -d $HASH2 &&
+     git show $HASH2 | grep "A U Thor" &&
+     test -z "$(git replace -l)"
+'
+
+test_expect_success '"git replace" replacing' '
+     git replace $HASH2 $R &&
+     git show $HASH2 | grep "O Thor" &&
+     test_must_fail git replace $HASH2 $R &&
+     git replace -f $HASH2 $R &&
+     test_must_fail git replace -f &&
+     test "$HASH2" = "$(git replace)"
+'
+
+# This creates a side branch where the bug in H2
+# does not appear because P2 is created by applying
+# H2 and squashing H5 into it.
+# P3, P4 and P6 are created by cherry-picking H3, H4
+# and H6 respectively.
+#
+# At this point, we should have the following:
+#
+#    P2--P3--P4--P6
+#   /
+# H1-H2-H3-H4-H5-H6-H7
+#
+# Then we replace H6 with P6.
+#
+test_expect_success 'create parallel branch without the bug' '
+     git replace -d $HASH2 &&
+     git show $HASH2 | grep "A U Thor" &&
+     git checkout $HASH1 &&
+     git cherry-pick $HASH2 &&
+     git show $HASH5 | git apply &&
+     git commit --amend -m "hello: 4 more lines WITHOUT the bug" hello &&
+     PARA2=$(git rev-parse --verify HEAD) &&
+     git cherry-pick $HASH3 &&
+     PARA3=$(git rev-parse --verify HEAD) &&
+     git cherry-pick $HASH4 &&
+     PARA4=$(git rev-parse --verify HEAD) &&
+     git cherry-pick $HASH6 &&
+     PARA6=$(git rev-parse --verify HEAD) &&
+     git replace $HASH6 $PARA6 &&
+     git checkout master &&
+     cur=$(git rev-parse --verify HEAD) &&
+     test "$cur" = "$HASH7" &&
+     git log --pretty=oneline | grep $PARA2 &&
+     git remote add cloned ./clone_dir
+'
+
+test_expect_success 'push to cloned repo' '
+     git push cloned $HASH6^:refs/heads/parallel &&
+     cd clone_dir &&
+     git checkout parallel &&
+     git log --pretty=oneline | grep $PARA2 &&
+     cd ..
+'
+
+test_expect_success 'push branch with replacement' '
+     git cat-file commit $PARA3 | grep "author A U Thor" &&
+     S=$(git cat-file commit $PARA3 | sed -e "s/A U/O/" | git hash-object -t commit --stdin -w) &&
+     git cat-file commit $S | grep "author O Thor" &&
+     git replace $PARA3 $S &&
+     git show $HASH6~2 | grep "O Thor" &&
+     git show $PARA3 | grep "O Thor" &&
+     git push cloned $HASH6^:refs/heads/parallel2 &&
+     cd clone_dir &&
+     git checkout parallel2 &&
+     git log --pretty=oneline | grep $PARA3 &&
+     git show $PARA3 | grep "A U Thor" &&
+     cd ..
+'
+
+test_expect_success 'fetch branch with replacement' '
+     git branch tofetch $HASH6 &&
+     cd clone_dir &&
+     git fetch origin refs/heads/tofetch:refs/heads/parallel3
+     git log --pretty=oneline parallel3 | grep $PARA3
+     git show $PARA3 | grep "A U Thor"
+     cd ..
+'
+
+#
+#
+test_done

upload-pack.c

@@ -651,6 +651,7 @@ int main(int argc, char **argv)
 	int strict = 0;
 
 	git_extract_argv0_path(argv[0]);
+	read_replace_refs = 0;
 
 	for (i = 1; i < argc; i++) {
 		char *arg = argv[i];