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-rw-r--r--branch.c5
-rw-r--r--builtin/commit.c4
-rw-r--r--builtin/fetch.c6
-rw-r--r--builtin/receive-pack.c5
-rw-r--r--builtin/replace.c2
-rw-r--r--builtin/tag.c2
-rw-r--r--builtin/update-ref.c20
-rw-r--r--cache.h2
-rw-r--r--fast-import.c6
-rw-r--r--refs.c140
-rw-r--r--refs.h113
-rw-r--r--sequencer.c2
-rwxr-xr-xt/t7516-commit-races.sh30
-rw-r--r--walker.c2
14 files changed, 233 insertions, 106 deletions
diff --git a/branch.c b/branch.c
index 4bab55a..b002435 100644
--- a/branch.c
+++ b/branch.c
@@ -284,8 +284,9 @@ void create_branch(const char *head,
transaction = ref_transaction_begin(&err);
if (!transaction ||
- ref_transaction_update(transaction, ref.buf, sha1,
- null_sha1, 0, !forcing, msg, &err) ||
+ ref_transaction_update(transaction, ref.buf,
+ sha1, forcing ? NULL : null_sha1,
+ 0, msg, &err) ||
ref_transaction_commit(transaction, &err))
die("%s", err.buf);
ref_transaction_free(transaction);
diff --git a/builtin/commit.c b/builtin/commit.c
index 6055c76..961e467 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1766,8 +1766,8 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
if (!transaction ||
ref_transaction_update(transaction, "HEAD", sha1,
current_head
- ? current_head->object.sha1 : NULL,
- 0, !!current_head, sb.buf, &err) ||
+ ? current_head->object.sha1 : null_sha1,
+ 0, sb.buf, &err) ||
ref_transaction_commit(transaction, &err)) {
rollback_index_files();
die("%s", err.buf);
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 75a55e5..f951265 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -415,8 +415,10 @@ static int s_update_ref(const char *action,
transaction = ref_transaction_begin(&err);
if (!transaction ||
- ref_transaction_update(transaction, ref->name, ref->new_sha1,
- ref->old_sha1, 0, check_old, msg, &err))
+ ref_transaction_update(transaction, ref->name,
+ ref->new_sha1,
+ check_old ? ref->old_sha1 : NULL,
+ 0, msg, &err))
goto fail;
ret = ref_transaction_commit(transaction, &err);
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index e0ce78e..70e9ce5 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -953,8 +953,7 @@ static const char *update(struct command *cmd, struct shallow_info *si)
if (ref_transaction_delete(transaction,
namespaced_name,
old_sha1,
- 0, old_sha1 != NULL,
- "push", &err)) {
+ 0, "push", &err)) {
rp_error("%s", err.buf);
strbuf_release(&err);
return "failed to delete";
@@ -971,7 +970,7 @@ static const char *update(struct command *cmd, struct shallow_info *si)
if (ref_transaction_update(transaction,
namespaced_name,
new_sha1, old_sha1,
- 0, 1, "push",
+ 0, "push",
&err)) {
rp_error("%s", err.buf);
strbuf_release(&err);
diff --git a/builtin/replace.c b/builtin/replace.c
index 85d39b5..54bf01a 100644
--- a/builtin/replace.c
+++ b/builtin/replace.c
@@ -172,7 +172,7 @@ static int replace_object_sha1(const char *object_ref,
transaction = ref_transaction_begin(&err);
if (!transaction ||
ref_transaction_update(transaction, ref, repl, prev,
- 0, 1, NULL, &err) ||
+ 0, NULL, &err) ||
ref_transaction_commit(transaction, &err))
die("%s", err.buf);
diff --git a/builtin/tag.c b/builtin/tag.c
index 6dc85a9..4194b9a 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -733,7 +733,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
transaction = ref_transaction_begin(&err);
if (!transaction ||
ref_transaction_update(transaction, ref.buf, object, prev,
- 0, 1, NULL, &err) ||
+ 0, NULL, &err) ||
ref_transaction_commit(transaction, &err))
die("%s", err.buf);
ref_transaction_free(transaction);
diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 2497ba4..3d79a46 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -198,8 +198,9 @@ static const char *parse_cmd_update(struct ref_transaction *transaction,
if (*next != line_termination)
die("update %s: extra input: %s", refname, next);
- if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
- update_flags, have_old, msg, &err))
+ if (ref_transaction_update(transaction, refname,
+ new_sha1, have_old ? old_sha1 : NULL,
+ update_flags, msg, &err))
die("%s", err.buf);
update_flags = 0;
@@ -264,8 +265,9 @@ static const char *parse_cmd_delete(struct ref_transaction *transaction,
if (*next != line_termination)
die("delete %s: extra input: %s", refname, next);
- if (ref_transaction_delete(transaction, refname, old_sha1,
- update_flags, have_old, msg, &err))
+ if (ref_transaction_delete(transaction, refname,
+ have_old ? old_sha1 : NULL,
+ update_flags, msg, &err))
die("%s", err.buf);
update_flags = 0;
@@ -280,7 +282,6 @@ static const char *parse_cmd_verify(struct ref_transaction *transaction,
{
struct strbuf err = STRBUF_INIT;
char *refname;
- unsigned char new_sha1[20];
unsigned char old_sha1[20];
refname = parse_refname(input, &next);
@@ -291,13 +292,11 @@ static const char *parse_cmd_verify(struct ref_transaction *transaction,
PARSE_SHA1_OLD))
hashclr(old_sha1);
- hashcpy(new_sha1, old_sha1);
-
if (*next != line_termination)
die("verify %s: extra input: %s", refname, next);
- if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
- update_flags, 1, msg, &err))
+ if (ref_transaction_verify(transaction, refname, old_sha1,
+ update_flags, &err))
die("%s", err.buf);
update_flags = 0;
@@ -353,7 +352,8 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
{
const char *refname, *oldval;
unsigned char sha1[20], oldsha1[20];
- int delete = 0, no_deref = 0, read_stdin = 0, end_null = 0, flags = 0;
+ int delete = 0, no_deref = 0, read_stdin = 0, end_null = 0;
+ unsigned int flags = 0;
struct option options[] = {
OPT_STRING( 'm', NULL, &msg, N_("reason"), N_("reason of the update")),
OPT_BOOL('d', NULL, &delete, N_("delete the reference")),
diff --git a/cache.h b/cache.h
index 4d02efc..761c570 100644
--- a/cache.h
+++ b/cache.h
@@ -568,7 +568,7 @@ extern void update_index_if_able(struct index_state *, struct lock_file *);
extern int hold_locked_index(struct lock_file *, int);
extern void set_alternate_index_output(const char *);
-extern int delete_ref(const char *, const unsigned char *sha1, int delopt);
+extern int delete_ref(const char *, const unsigned char *sha1, unsigned int flags);
/* Environment bits from configuration mechanism */
extern int trust_executable_bit;
diff --git a/fast-import.c b/fast-import.c
index aac2c24..b82fcdd 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -1720,7 +1720,7 @@ static int update_branch(struct branch *b)
transaction = ref_transaction_begin(&err);
if (!transaction ||
ref_transaction_update(transaction, b->name, b->sha1, old_sha1,
- 0, 1, msg, &err) ||
+ 0, msg, &err) ||
ref_transaction_commit(transaction, &err)) {
ref_transaction_free(transaction);
error("%s", err.buf);
@@ -1760,8 +1760,8 @@ static void dump_tags(void)
strbuf_reset(&ref_name);
strbuf_addf(&ref_name, "refs/tags/%s", t->name);
- if (ref_transaction_update(transaction, ref_name.buf, t->sha1,
- NULL, 0, 0, msg, &err)) {
+ if (ref_transaction_update(transaction, ref_name.buf,
+ t->sha1, NULL, 0, msg, &err)) {
failure |= error("%s", err.buf);
goto cleanup;
}
diff --git a/refs.c b/refs.c
index ab2f2a9..8d46b08 100644
--- a/refs.c
+++ b/refs.c
@@ -35,10 +35,29 @@ static unsigned char refname_disposition[256] = {
};
/*
- * Used as a flag to ref_transaction_delete when a loose ref is being
+ * Flag passed to lock_ref_sha1_basic() telling it to tolerate broken
+ * refs (i.e., because the reference is about to be deleted anyway).
+ */
+#define REF_DELETING 0x02
+
+/*
+ * Used as a flag in ref_update::flags when a loose ref is being
* pruned.
*/
-#define REF_ISPRUNING 0x0100
+#define REF_ISPRUNING 0x04
+
+/*
+ * Used as a flag in ref_update::flags when the reference should be
+ * updated to new_sha1.
+ */
+#define REF_HAVE_NEW 0x08
+
+/*
+ * Used as a flag in ref_update::flags when old_sha1 should be
+ * checked.
+ */
+#define REF_HAVE_OLD 0x10
+
/*
* Try to read one refname component from the front of refname.
* Return the length of the component found, or -1 if the component is
@@ -2249,7 +2268,7 @@ int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
static struct ref_lock *lock_ref_sha1_basic(const char *refname,
const unsigned char *old_sha1,
const struct string_list *skip,
- int flags, int *type_p)
+ unsigned int flags, int *type_p)
{
char *ref_file;
const char *orig_refname = refname;
@@ -2563,7 +2582,7 @@ static void prune_ref(struct ref_to_prune *r)
transaction = ref_transaction_begin(&err);
if (!transaction ||
ref_transaction_delete(transaction, r->name, r->sha1,
- REF_ISPRUNING, 1, NULL, &err) ||
+ REF_ISPRUNING, NULL, &err) ||
ref_transaction_commit(transaction, &err)) {
ref_transaction_free(transaction);
error("%s", err.buf);
@@ -2733,15 +2752,16 @@ static int delete_ref_loose(struct ref_lock *lock, int flag, struct strbuf *err)
return 0;
}
-int delete_ref(const char *refname, const unsigned char *sha1, int delopt)
+int delete_ref(const char *refname, const unsigned char *sha1, unsigned int flags)
{
struct ref_transaction *transaction;
struct strbuf err = STRBUF_INIT;
transaction = ref_transaction_begin(&err);
if (!transaction ||
- ref_transaction_delete(transaction, refname, sha1, delopt,
- sha1 && !is_null_sha1(sha1), NULL, &err) ||
+ ref_transaction_delete(transaction, refname,
+ (sha1 && !is_null_sha1(sha1)) ? sha1 : NULL,
+ flags, NULL, &err) ||
ref_transaction_commit(transaction, &err)) {
error("%s", err.buf);
ref_transaction_free(transaction);
@@ -3556,16 +3576,27 @@ int for_each_reflog(each_ref_fn fn, void *cb_data)
}
/**
- * Information needed for a single ref update. Set new_sha1 to the
- * new value or to zero to delete the ref. To check the old value
- * while locking the ref, set have_old to 1 and set old_sha1 to the
- * value or to zero to ensure the ref does not exist before update.
+ * Information needed for a single ref update. Set new_sha1 to the new
+ * value or to null_sha1 to delete the ref. To check the old value
+ * while the ref is locked, set (flags & REF_HAVE_OLD) and set
+ * old_sha1 to the old value, or to null_sha1 to ensure the ref does
+ * not exist before update.
*/
struct ref_update {
+ /*
+ * If (flags & REF_HAVE_NEW), set the reference to this value:
+ */
unsigned char new_sha1[20];
+ /*
+ * If (flags & REF_HAVE_OLD), check that the reference
+ * previously had this value:
+ */
unsigned char old_sha1[20];
- int flags; /* REF_NODEREF? */
- int have_old; /* 1 if old_sha1 is valid, 0 otherwise */
+ /*
+ * One or more of REF_HAVE_NEW, REF_HAVE_OLD, REF_NODEREF,
+ * REF_DELETING, and REF_ISPRUNING:
+ */
+ unsigned int flags;
struct ref_lock *lock;
int type;
char *msg;
@@ -3637,7 +3668,7 @@ int ref_transaction_update(struct ref_transaction *transaction,
const char *refname,
const unsigned char *new_sha1,
const unsigned char *old_sha1,
- int flags, int have_old, const char *msg,
+ unsigned int flags, const char *msg,
struct strbuf *err)
{
struct ref_update *update;
@@ -3647,10 +3678,7 @@ int ref_transaction_update(struct ref_transaction *transaction,
if (transaction->state != REF_TRANSACTION_OPEN)
die("BUG: update called for transaction that is not open");
- if (have_old && !old_sha1)
- die("BUG: have_old is true but old_sha1 is NULL");
-
- if (!is_null_sha1(new_sha1) &&
+ if (new_sha1 && !is_null_sha1(new_sha1) &&
check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
strbuf_addf(err, "refusing to update ref with bad name %s",
refname);
@@ -3658,11 +3686,15 @@ int ref_transaction_update(struct ref_transaction *transaction,
}
update = add_update(transaction, refname);
- hashcpy(update->new_sha1, new_sha1);
- update->flags = flags;
- update->have_old = have_old;
- if (have_old)
+ if (new_sha1) {
+ hashcpy(update->new_sha1, new_sha1);
+ flags |= REF_HAVE_NEW;
+ }
+ if (old_sha1) {
hashcpy(update->old_sha1, old_sha1);
+ flags |= REF_HAVE_OLD;
+ }
+ update->flags = flags;
if (msg)
update->msg = xstrdup(msg);
return 0;
@@ -3671,34 +3703,52 @@ int ref_transaction_update(struct ref_transaction *transaction,
int ref_transaction_create(struct ref_transaction *transaction,
const char *refname,
const unsigned char *new_sha1,
- int flags, const char *msg,
+ unsigned int flags, const char *msg,
struct strbuf *err)
{
+ if (!new_sha1 || is_null_sha1(new_sha1))
+ die("BUG: create called without valid new_sha1");
return ref_transaction_update(transaction, refname, new_sha1,
- null_sha1, flags, 1, msg, err);
+ null_sha1, flags, msg, err);
}
int ref_transaction_delete(struct ref_transaction *transaction,
const char *refname,
const unsigned char *old_sha1,
- int flags, int have_old, const char *msg,
+ unsigned int flags, const char *msg,
struct strbuf *err)
{
- return ref_transaction_update(transaction, refname, null_sha1,
- old_sha1, flags, have_old, msg, err);
+ if (old_sha1 && is_null_sha1(old_sha1))
+ die("BUG: delete called with old_sha1 set to zeros");
+ return ref_transaction_update(transaction, refname,
+ null_sha1, old_sha1,
+ flags, msg, err);
}
-int update_ref(const char *action, const char *refname,
- const unsigned char *sha1, const unsigned char *oldval,
- int flags, enum action_on_err onerr)
+int ref_transaction_verify(struct ref_transaction *transaction,
+ const char *refname,
+ const unsigned char *old_sha1,
+ unsigned int flags,
+ struct strbuf *err)
+{
+ if (!old_sha1)
+ die("BUG: verify called with old_sha1 set to NULL");
+ return ref_transaction_update(transaction, refname,
+ NULL, old_sha1,
+ flags, NULL, err);
+}
+
+int update_ref(const char *msg, const char *refname,
+ const unsigned char *new_sha1, const unsigned char *old_sha1,
+ unsigned int flags, enum action_on_err onerr)
{
struct ref_transaction *t;
struct strbuf err = STRBUF_INIT;
t = ref_transaction_begin(&err);
if (!t ||
- ref_transaction_update(t, refname, sha1, oldval, flags,
- !!oldval, action, &err) ||
+ ref_transaction_update(t, refname, new_sha1, old_sha1,
+ flags, msg, &err) ||
ref_transaction_commit(t, &err)) {
const char *str = "update_ref failed for ref '%s': %s";
@@ -3774,17 +3824,17 @@ int ref_transaction_commit(struct ref_transaction *transaction,
/* Acquire all locks while verifying old values */
for (i = 0; i < n; i++) {
struct ref_update *update = updates[i];
- int flags = update->flags;
+ unsigned int flags = update->flags;
- if (is_null_sha1(update->new_sha1))
+ if ((flags & REF_HAVE_NEW) && is_null_sha1(update->new_sha1))
flags |= REF_DELETING;
- update->lock = lock_ref_sha1_basic(update->refname,
- (update->have_old ?
- update->old_sha1 :
- NULL),
- NULL,
- flags,
- &update->type);
+ update->lock = lock_ref_sha1_basic(
+ update->refname,
+ ((update->flags & REF_HAVE_OLD) ?
+ update->old_sha1 : NULL),
+ NULL,
+ flags,
+ &update->type);
if (!update->lock) {
ret = (errno == ENOTDIR)
? TRANSACTION_NAME_CONFLICT
@@ -3798,8 +3848,9 @@ int ref_transaction_commit(struct ref_transaction *transaction,
/* Perform updates first so live commits remain referenced */
for (i = 0; i < n; i++) {
struct ref_update *update = updates[i];
+ int flags = update->flags;
- if (!is_null_sha1(update->new_sha1)) {
+ if ((flags & REF_HAVE_NEW) && !is_null_sha1(update->new_sha1)) {
if (write_ref_sha1(update->lock, update->new_sha1,
update->msg)) {
update->lock = NULL; /* freed by write_ref_sha1 */
@@ -3815,14 +3866,15 @@ int ref_transaction_commit(struct ref_transaction *transaction,
/* Perform deletes now that updates are safely completed */
for (i = 0; i < n; i++) {
struct ref_update *update = updates[i];
+ int flags = update->flags;
- if (update->lock) {
+ if ((flags & REF_HAVE_NEW) && is_null_sha1(update->new_sha1)) {
if (delete_ref_loose(update->lock, update->type, err)) {
ret = TRANSACTION_GENERIC_ERROR;
goto cleanup;
}
- if (!(update->flags & REF_ISPRUNING))
+ if (!(flags & REF_ISPRUNING))
string_list_append(&refs_to_delete,
update->lock->ref_name);
}
diff --git a/refs.h b/refs.h
index afa3c4d..cf642e6 100644
--- a/refs.h
+++ b/refs.h
@@ -183,12 +183,10 @@ extern int peel_ref(const char *refname, unsigned char *sha1);
* Flags controlling ref_transaction_update(), ref_transaction_create(), etc.
* REF_NODEREF: act on the ref directly, instead of dereferencing
* symbolic references.
- * REF_DELETING: tolerate broken refs
*
- * Flags >= 0x100 are reserved for internal use.
+ * Other flags are reserved for internal use.
*/
#define REF_NODEREF 0x01
-#define REF_DELETING 0x02
/*
* Setup reflog before using. Set errno to something meaningful on failure.
@@ -257,57 +255,95 @@ enum action_on_err {
struct ref_transaction *ref_transaction_begin(struct strbuf *err);
/*
- * The following functions add a reference check or update to a
- * ref_transaction. In all of them, refname is the name of the
- * reference to be affected. The functions make internal copies of
- * refname and msg, so the caller retains ownership of these parameters.
- * flags can be REF_NODEREF; it is passed to update_ref_lock().
+ * Reference transaction updates
+ *
+ * The following four functions add a reference check or update to a
+ * ref_transaction. They have some common similar parameters:
+ *
+ * transaction -- a pointer to an open ref_transaction, obtained
+ * from ref_transaction_begin().
+ *
+ * refname -- the name of the reference to be affected.
+ *
+ * flags -- flags affecting the update, passed to
+ * update_ref_lock(). Can be REF_NODEREF, which means that
+ * symbolic references should not be followed.
+ *
+ * msg -- a message describing the change (for the reflog).
+ *
+ * err -- a strbuf for receiving a description of any error that
+ * might have occured.
+ *
+ * The functions make internal copies of refname and msg, so the
+ * caller retains ownership of these parameters.
+ *
+ * The functions return 0 on success and non-zero on failure. A
+ * failure means that the transaction as a whole has failed and needs
+ * to be rolled back.
*/
/*
- * Add a reference update to transaction. new_sha1 is the value that
- * the reference should have after the update, or null_sha1 if it should
- * be deleted. If have_old is true, then old_sha1 holds the value
- * that the reference should have had before the update, or zeros if
- * it must not have existed beforehand.
- * Function returns 0 on success and non-zero on failure. A failure to update
- * means that the transaction as a whole has failed and will need to be
- * rolled back.
+ * Add a reference update to transaction. new_sha1 is the value that
+ * the reference should have after the update, or null_sha1 if it
+ * should be deleted. If new_sha1 is NULL, then the reference is not
+ * changed at all. old_sha1 is the value that the reference must have
+ * before the update, or null_sha1 if it must not have existed
+ * beforehand. The old value is checked after the lock is taken to
+ * prevent races. If the old value doesn't agree with old_sha1, the
+ * whole transaction fails. If old_sha1 is NULL, then the previous
+ * value is not checked.
+ *
+ * See the above comment "Reference transaction updates" for more
+ * information.
*/
int ref_transaction_update(struct ref_transaction *transaction,
const char *refname,
const unsigned char *new_sha1,
const unsigned char *old_sha1,
- int flags, int have_old, const char *msg,
+ unsigned int flags, const char *msg,
struct strbuf *err);
/*
- * Add a reference creation to transaction. new_sha1 is the value
- * that the reference should have after the update; it must not be the
- * null SHA-1. It is verified that the reference does not exist
+ * Add a reference creation to transaction. new_sha1 is the value that
+ * the reference should have after the update; it must not be
+ * null_sha1. It is verified that the reference does not exist
* already.
- * Function returns 0 on success and non-zero on failure. A failure to create
- * means that the transaction as a whole has failed and will need to be
- * rolled back.
+ *
+ * See the above comment "Reference transaction updates" for more
+ * information.
*/
int ref_transaction_create(struct ref_transaction *transaction,
const char *refname,
const unsigned char *new_sha1,
- int flags, const char *msg,
+ unsigned int flags, const char *msg,
struct strbuf *err);
/*
- * Add a reference deletion to transaction. If have_old is true, then
- * old_sha1 holds the value that the reference should have had before
- * the update (which must not be the null SHA-1).
- * Function returns 0 on success and non-zero on failure. A failure to delete
- * means that the transaction as a whole has failed and will need to be
- * rolled back.
+ * Add a reference deletion to transaction. If old_sha1 is non-NULL,
+ * then it holds the value that the reference should have had before
+ * the update (which must not be null_sha1).
+ *
+ * See the above comment "Reference transaction updates" for more
+ * information.
*/
int ref_transaction_delete(struct ref_transaction *transaction,
const char *refname,
const unsigned char *old_sha1,
- int flags, int have_old, const char *msg,
+ unsigned int flags, const char *msg,
+ struct strbuf *err);
+
+/*
+ * Verify, within a transaction, that refname has the value old_sha1,
+ * or, if old_sha1 is null_sha1, then verify that the reference
+ * doesn't exist. old_sha1 must be non-NULL.
+ *
+ * See the above comment "Reference transaction updates" for more
+ * information.
+ */
+int ref_transaction_verify(struct ref_transaction *transaction,
+ const char *refname,
+ const unsigned char *old_sha1,
+ unsigned int flags,
struct strbuf *err);
/*
@@ -328,10 +364,17 @@ int ref_transaction_commit(struct ref_transaction *transaction,
*/
void ref_transaction_free(struct ref_transaction *transaction);
-/** Lock a ref and then write its file */
-int update_ref(const char *action, const char *refname,
- const unsigned char *sha1, const unsigned char *oldval,
- int flags, enum action_on_err onerr);
+/**
+ * Lock, update, and unlock a single reference. This function
+ * basically does a transaction containing a single call to
+ * ref_transaction_update(). The parameters to this function have the
+ * same meaning as the corresponding parameters to
+ * ref_transaction_update(). Handle errors as requested by the `onerr`
+ * argument.
+ */
+int update_ref(const char *msg, const char *refname,
+ const unsigned char *new_sha1, const unsigned char *old_sha1,
+ unsigned int flags, enum action_on_err onerr);
extern int parse_hide_refs_config(const char *var, const char *value, const char *);
extern int ref_is_hidden(const char *);
diff --git a/sequencer.c b/sequencer.c
index 77a1266..32aa05e 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -252,7 +252,7 @@ static int fast_forward_to(const unsigned char *to, const unsigned char *from,
if (!transaction ||
ref_transaction_update(transaction, "HEAD",
to, unborn ? null_sha1 : from,
- 0, 1, sb.buf, &err) ||
+ 0, sb.buf, &err) ||
ref_transaction_commit(transaction, &err)) {
ref_transaction_free(transaction);
error("%s", err.buf);
diff --git a/t/t7516-commit-races.sh b/t/t7516-commit-races.sh
new file mode 100755
index 0000000..f2ce14e
--- /dev/null
+++ b/t/t7516-commit-races.sh
@@ -0,0 +1,30 @@
+#!/bin/sh
+
+test_description='git commit races'
+. ./test-lib.sh
+
+test_expect_success 'race to create orphan commit' '
+ write_script hare-editor <<-\EOF &&
+ git commit --allow-empty -m hare
+ EOF
+ test_must_fail env EDITOR=./hare-editor git commit --allow-empty -m tortoise -e &&
+ git show -s --pretty=format:%s >subject &&
+ grep hare subject &&
+ test -z "$(git show -s --pretty=format:%P)"
+'
+
+test_expect_success 'race to create non-orphan commit' '
+ write_script airplane-editor <<-\EOF &&
+ git commit --allow-empty -m airplane
+ EOF
+ git checkout --orphan branch &&
+ git commit --allow-empty -m base &&
+ git rev-parse HEAD >base &&
+ test_must_fail env EDITOR=./airplane-editor git commit --allow-empty -m ship -e &&
+ git show -s --pretty=format:%s >subject &&
+ grep airplane subject &&
+ git rev-parse HEAD^ >parent &&
+ test_cmp base parent
+'
+
+test_done
diff --git a/walker.c b/walker.c
index 483da4e..58ffeca 100644
--- a/walker.c
+++ b/walker.c
@@ -299,7 +299,7 @@ int walker_fetch(struct walker *walker, int targets, char **target,
strbuf_reset(&refname);
strbuf_addf(&refname, "refs/%s", write_ref[i]);
if (ref_transaction_update(transaction, refname.buf,
- &sha1[20 * i], NULL, 0, 0,
+ &sha1[20 * i], NULL, 0,
msg ? msg : "fetch (unknown)",
&err)) {
error("%s", err.buf);