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ref_transaction_verify(): new function to check a reference's value

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If NULL is passed to ref_transaction_update()'s new_sha1 parameter,
then just verify old_sha1 (under lock) without trying to change the
new value of the reference.

Use this functionality to add a new function ref_transaction_verify(),
which checks the current value of the reference under lock but doesn't
change it.

Use ref_transaction_verify() in the implementation of "git update-ref
--stdin"'s "verify" command to avoid the awkward need to "update" the
reference to its existing value.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Michael Haggerty 2015-02-17 18:00:21 +01:00 committed by Junio C Hamano
parent 60294596ba
commit 1618033401
3 changed files with 67 additions and 21 deletions
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7
builtin/update-ref.c
View File

@ -282,7 +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);
@ -293,13 +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, msg, &err))
if (ref_transaction_verify(transaction, refname, old_sha1,
update_flags, &err))
die("%s", err.buf);
update_flags = 0;

47
refs.c
View File

@ -46,11 +46,17 @@ static unsigned char refname_disposition[256] = {
*/
#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 0x08
#define REF_HAVE_OLD 0x10
/*
* Try to read one refname component from the front of refname.
@ -3577,10 +3583,17 @@ int for_each_reflog(each_ref_fn fn, void *cb_data)
* 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];
/*
* One or more of REF_HAVE_OLD, REF_NODEREF,
* One or more of REF_HAVE_NEW, REF_HAVE_OLD, REF_NODEREF,
* REF_DELETING, and REF_ISPRUNING:
*/
unsigned int flags;
@ -3665,7 +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 (!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);
@ -3673,7 +3686,10 @@ int ref_transaction_update(struct ref_transaction *transaction,
}
update = add_update(transaction, refname);
hashcpy(update->new_sha1, new_sha1);
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;
@ -3709,6 +3725,19 @@ int ref_transaction_delete(struct ref_transaction *transaction,
flags, msg, err);
}
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 *action, const char *refname,
const unsigned char *sha1, const unsigned char *oldval,
unsigned int flags, enum action_on_err onerr)
@ -3797,7 +3826,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
struct ref_update *update = updates[i];
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,
@ -3819,8 +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 */
@ -3836,14 +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);
}

34
refs.h
View File

@ -263,14 +263,19 @@ struct ref_transaction *ref_transaction_begin(struct strbuf *err);
*/
/*
* 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 old_sha1 is non-NULL, then it is the value
* that the reference should have had before the update, or null_sha1 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.
*
* Return 0 on success and non-zero on failure. Any failure in the
* transaction means that the transaction as a whole has failed and
* will need to be rolled back.
*/
int ref_transaction_update(struct ref_transaction *transaction,
const char *refname,
@ -308,6 +313,19 @@ int ref_transaction_delete(struct ref_transaction *transaction,
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. Function returns 0 on
* success and non-zero on failure. A failure to verify means that the
* transaction as a whole has failed and will need to be rolled back.
*/
int ref_transaction_verify(struct ref_transaction *transaction,
const char *refname,
const unsigned char *old_sha1,
unsigned int flags,
struct strbuf *err);
/*
* Commit all of the changes that have been queued in transaction, as
* atomically as possible.