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* Builtin "git replace"
* Copyright (c) 2008 Christian Couder <>
* Based on builtin/tag.c by Kristian Høgsberg <>
* and Carlos Rica <> that was itself based on
* and mktag.c by Linus Torvalds.
#include "cache.h"
#include "config.h"
#include "builtin.h"
#include "refs.h"
#include "parse-options.h"
#include "run-command.h"
#include "tag.h"
static const char * const git_replace_usage[] = {
N_("git replace [-f] <object> <replacement>"),
N_("git replace [-f] --edit <object>"),
N_("git replace [-f] --graft <commit> [<parent>...]"),
N_("git replace -d <object>..."),
N_("git replace [--format=<format>] [-l [<pattern>]]"),
enum replace_format {
struct show_data {
const char *pattern;
enum replace_format format;
static int show_reference(const char *refname, const struct object_id *oid,
int flag, void *cb_data)
struct show_data *data = cb_data;
if (!wildmatch(data->pattern, refname, 0)) {
if (data->format == REPLACE_FORMAT_SHORT)
printf("%s\n", refname);
else if (data->format == REPLACE_FORMAT_MEDIUM)
printf("%s -> %s\n", refname, oid_to_hex(oid));
else { /* data->format == REPLACE_FORMAT_LONG */
struct object_id object;
enum object_type obj_type, repl_type;
if (get_sha1(refname, object.hash))
return error("Failed to resolve '%s' as a valid ref.", refname);
obj_type = sha1_object_info(object.hash, NULL);
repl_type = sha1_object_info(oid->hash, NULL);
printf("%s (%s) -> %s (%s)\n", refname, typename(obj_type),
oid_to_hex(oid), typename(repl_type));
return 0;
static int list_replace_refs(const char *pattern, const char *format)
struct show_data data;
if (pattern == NULL)
pattern = "*";
data.pattern = pattern;
if (format == NULL || *format == '\0' || !strcmp(format, "short"))
else if (!strcmp(format, "medium"))
else if (!strcmp(format, "long"))
data.format = REPLACE_FORMAT_LONG;
die("invalid replace format '%s'\n"
"valid formats are 'short', 'medium' and 'long'\n",
for_each_replace_ref(show_reference, (void *)&data);
return 0;
typedef int (*each_replace_name_fn)(const char *name, const char *ref,
const struct object_id *oid);
static int for_each_replace_name(const char **argv, each_replace_name_fn fn)
const char **p, *full_hex;
struct strbuf ref = STRBUF_INIT;
size_t base_len;
int had_error = 0;
struct object_id oid;
strbuf_addstr(&ref, git_replace_ref_base);
base_len = ref.len;
for (p = argv; *p; p++) {
if (get_oid(*p, &oid)) {
error("Failed to resolve '%s' as a valid ref.", *p);
had_error = 1;
strbuf_setlen(&ref, base_len);
strbuf_addstr(&ref, oid_to_hex(&oid));
full_hex = ref.buf + base_len;
if (read_ref(ref.buf, oid.hash)) {
error("replace ref '%s' not found.", full_hex);
had_error = 1;
if (fn(full_hex, ref.buf, &oid))
had_error = 1;
return had_error;
static int delete_replace_ref(const char *name, const char *ref,
const struct object_id *oid)
if (delete_ref(NULL, ref, oid->hash, 0))
return 1;
printf("Deleted replace ref '%s'\n", name);
return 0;
static void check_ref_valid(struct object_id *object,
struct object_id *prev,
struct strbuf *ref,
int force)
strbuf_addf(ref, "%s%s", git_replace_ref_base, oid_to_hex(object));
if (check_refname_format(ref->buf, 0))
die("'%s' is not a valid ref name.", ref->buf);
if (read_ref(ref->buf, prev->hash))
else if (!force)
die("replace ref '%s' already exists", ref->buf);
static int replace_object_oid(const char *object_ref,
struct object_id *object,
const char *replace_ref,
struct object_id *repl,
int force)
struct object_id prev;
enum object_type obj_type, repl_type;
struct strbuf ref = STRBUF_INIT;
struct ref_transaction *transaction;
struct strbuf err = STRBUF_INIT;
obj_type = sha1_object_info(object->hash, NULL);
repl_type = sha1_object_info(repl->hash, NULL);
if (!force && obj_type != repl_type)
die("Objects must be of the same type.\n"
"'%s' points to a replaced object of type '%s'\n"
"while '%s' points to a replacement object of type '%s'.",
object_ref, typename(obj_type),
replace_ref, typename(repl_type));
check_ref_valid(object, &prev, &ref, force);
transaction = ref_transaction_begin(&err);
if (!transaction ||
ref_transaction_update(transaction, ref.buf, repl->hash, prev.hash,
0, NULL, &err) ||
ref_transaction_commit(transaction, &err))
die("%s", err.buf);
return 0;
static int replace_object(const char *object_ref, const char *replace_ref, int force)
struct object_id object, repl;
if (get_oid(object_ref, &object))
die("Failed to resolve '%s' as a valid ref.", object_ref);
if (get_oid(replace_ref, &repl))
die("Failed to resolve '%s' as a valid ref.", replace_ref);
return replace_object_oid(object_ref, &object, replace_ref, &repl, force);
* Write the contents of the object named by "sha1" to the file "filename".
* If "raw" is true, then the object's raw contents are printed according to
* "type". Otherwise, we pretty-print the contents for human editing.
static void export_object(const struct object_id *oid, enum object_type type,
int raw, const char *filename)
struct child_process cmd = CHILD_PROCESS_INIT;
int fd;
fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
if (fd < 0)
die_errno("unable to open %s for writing", filename);
argv_array_push(&cmd.args, "--no-replace-objects");
argv_array_push(&cmd.args, "cat-file");
if (raw)
argv_array_push(&cmd.args, typename(type));
argv_array_push(&cmd.args, "-p");
argv_array_push(&cmd.args, oid_to_hex(oid));
cmd.git_cmd = 1;
cmd.out = fd;
if (run_command(&cmd))
die("cat-file reported failure");
* Read a previously-exported (and possibly edited) object back from "filename",
* interpreting it as "type", and writing the result to the object database.
* The sha1 of the written object is returned via sha1.
static void import_object(struct object_id *oid, enum object_type type,
int raw, const char *filename)
int fd;
fd = open(filename, O_RDONLY);
if (fd < 0)
die_errno("unable to open %s for reading", filename);
if (!raw && type == OBJ_TREE) {
const char *argv[] = { "mktree", NULL };
struct child_process cmd = CHILD_PROCESS_INIT;
struct strbuf result = STRBUF_INIT;
cmd.argv = argv;
cmd.git_cmd = 1; = fd;
cmd.out = -1;
if (start_command(&cmd))
die("unable to spawn mktree");
if (strbuf_read(&result, cmd.out, 41) < 0)
die_errno("unable to read from mktree");
if (finish_command(&cmd))
die("mktree reported failure");
if (get_oid_hex(result.buf, oid) < 0)
die("mktree did not return an object name");
} else {
struct stat st;
if (fstat(fd, &st) < 0)
die_errno("unable to fstat %s", filename);
if (index_fd(oid->hash, fd, &st, type, NULL, flags) < 0)
die("unable to write object to database");
/* index_fd close()s fd for us */
* No need to close(fd) here; both run-command and index-fd
* will have done it for us.
static int edit_and_replace(const char *object_ref, int force, int raw)
char *tmpfile = git_pathdup("REPLACE_EDITOBJ");
enum object_type type;
struct object_id old, new, prev;
struct strbuf ref = STRBUF_INIT;
if (get_oid(object_ref, &old) < 0)
die("Not a valid object name: '%s'", object_ref);
type = sha1_object_info(old.hash, NULL);
if (type < 0)
die("unable to get object type for %s", oid_to_hex(&old));
check_ref_valid(&old, &prev, &ref, force);
export_object(&old, type, raw, tmpfile);
if (launch_editor(tmpfile, NULL, NULL) < 0)
die("editing object file failed");
import_object(&new, type, raw, tmpfile);
if (!oidcmp(&old, &new))
return error("new object is the same as the old one: '%s'", oid_to_hex(&old));
return replace_object_oid(object_ref, &old, "replacement", &new, force);
static void replace_parents(struct strbuf *buf, int argc, const char **argv)
struct strbuf new_parents = STRBUF_INIT;
const char *parent_start, *parent_end;
int i;
/* find existing parents */
parent_start = buf->buf;
parent_start += GIT_SHA1_HEXSZ + 6; /* "tree " + "hex sha1" + "\n" */
parent_end = parent_start;
while (starts_with(parent_end, "parent "))
parent_end += 48; /* "parent " + "hex sha1" + "\n" */
/* prepare new parents */
for (i = 0; i < argc; i++) {
struct object_id oid;
if (get_oid(argv[i], &oid) < 0)
die(_("Not a valid object name: '%s'"), argv[i]);
lookup_commit_or_die(&oid, argv[i]);
strbuf_addf(&new_parents, "parent %s\n", oid_to_hex(&oid));
/* replace existing parents with new ones */
strbuf_splice(buf, parent_start - buf->buf, parent_end - parent_start,
new_parents.buf, new_parents.len);
struct check_mergetag_data {
int argc;
const char **argv;
static void check_one_mergetag(struct commit *commit,
struct commit_extra_header *extra,
void *data)
struct check_mergetag_data *mergetag_data = (struct check_mergetag_data *)data;
const char *ref = mergetag_data->argv[0];
struct object_id tag_oid;
struct tag *tag;
int i;
hash_sha1_file(extra->value, extra->len, typename(OBJ_TAG), tag_oid.hash);
tag = lookup_tag(&tag_oid);
if (!tag)
die(_("bad mergetag in commit '%s'"), ref);
if (parse_tag_buffer(tag, extra->value, extra->len))
die(_("malformed mergetag in commit '%s'"), ref);
/* iterate over new parents */
for (i = 1; i < mergetag_data->argc; i++) {
struct object_id oid;
if (get_sha1(mergetag_data->argv[i], oid.hash) < 0)
die(_("Not a valid object name: '%s'"), mergetag_data->argv[i]);
if (!oidcmp(&tag->tagged->oid, &oid))
return; /* found */
die(_("original commit '%s' contains mergetag '%s' that is discarded; "
"use --edit instead of --graft"), ref, oid_to_hex(&tag_oid));
static void check_mergetags(struct commit *commit, int argc, const char **argv)
struct check_mergetag_data mergetag_data;
mergetag_data.argc = argc;
mergetag_data.argv = argv;
for_each_mergetag(check_one_mergetag, commit, &mergetag_data);
static int create_graft(int argc, const char **argv, int force)
struct object_id old, new;
const char *old_ref = argv[0];
struct commit *commit;
struct strbuf buf = STRBUF_INIT;
const char *buffer;
unsigned long size;
if (get_oid(old_ref, &old) < 0)
die(_("Not a valid object name: '%s'"), old_ref);
commit = lookup_commit_or_die(&old, old_ref);
buffer = get_commit_buffer(commit, &size);
strbuf_add(&buf, buffer, size);
unuse_commit_buffer(commit, buffer);
replace_parents(&buf, argc - 1, &argv[1]);
if (remove_signature(&buf)) {
warning(_("the original commit '%s' has a gpg signature."), old_ref);
warning(_("the signature will be removed in the replacement commit!"));
check_mergetags(commit, argc, argv);
if (write_sha1_file(buf.buf, buf.len, commit_type, new.hash))
die(_("could not write replacement commit for: '%s'"), old_ref);
if (!oidcmp(&old, &new))
return error("new commit is the same as the old one: '%s'", oid_to_hex(&old));
return replace_object_oid(old_ref, &old, "replacement", &new, force);
int cmd_replace(int argc, const char **argv, const char *prefix)
int force = 0;
int raw = 0;
const char *format = NULL;
enum {
struct option options[] = {
OPT_CMDMODE('l', "list", &cmdmode, N_("list replace refs"), MODE_LIST),
OPT_CMDMODE('d', "delete", &cmdmode, N_("delete replace refs"), MODE_DELETE),
OPT_CMDMODE('e', "edit", &cmdmode, N_("edit existing object"), MODE_EDIT),
OPT_CMDMODE('g', "graft", &cmdmode, N_("change a commit's parents"), MODE_GRAFT),
OPT_BOOL('f', "force", &force, N_("replace the ref if it exists")),
OPT_BOOL(0, "raw", &raw, N_("do not pretty-print contents for --edit")),
OPT_STRING(0, "format", &format, N_("format"), N_("use this format")),
check_replace_refs = 0;
git_config(git_default_config, NULL);
argc = parse_options(argc, argv, prefix, options, git_replace_usage, 0);
if (!cmdmode)
cmdmode = argc ? MODE_REPLACE : MODE_LIST;
if (format && cmdmode != MODE_LIST)
usage_msg_opt("--format cannot be used when not listing",
git_replace_usage, options);
if (force &&
cmdmode != MODE_REPLACE &&
cmdmode != MODE_EDIT &&
cmdmode != MODE_GRAFT)
usage_msg_opt("-f only makes sense when writing a replacement",
git_replace_usage, options);
if (raw && cmdmode != MODE_EDIT)
usage_msg_opt("--raw only makes sense with --edit",
git_replace_usage, options);
switch (cmdmode) {
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);
if (argc != 2)
usage_msg_opt("bad number of arguments",
git_replace_usage, options);
return replace_object(argv[0], argv[1], force);
if (argc != 1)
usage_msg_opt("-e needs exactly one argument",
git_replace_usage, options);
return edit_and_replace(argv[0], force, raw);
if (argc < 1)
usage_msg_opt("-g needs at least one argument",
git_replace_usage, options);
return create_graft(argc, argv, force);
if (argc > 1)
usage_msg_opt("only one pattern can be given with -l",
git_replace_usage, options);
return list_replace_refs(argv[0], format);
die("BUG: invalid cmdmode %d", (int)cmdmode);