sequencer.c: use ref transactions for all ref updates

Change to use ref transactions for all updates to refs.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
fast-import.c: change update_branch to use ref transactions

Change update_branch() to use ref transactions for updates.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
branch.c: use ref transaction for all ref updates

Change create_branch to use a ref transaction when creating the new branch.

This also fixes a race condition in the old code where two concurrent
create_branch could race since the lock_any_ref_for_update/write_ref_sha1
did not protect against the ref already existing. I.e. one thread could end up
overwriting a branch even if the forcing flag is false.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: change update_ref to use a transaction

Change the update_ref helper function to use a ref transaction internally.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
receive-pack.c: use a reference transaction for updating the refs

Wrap all the ref updates inside a transaction.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
fast-import.c: use a ref transaction when dumping tags

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
walker.c: use ref transaction for ref updates

Switch to using ref transactions in walker_fetch(). As part of the refactoring
to use ref transactions we also fix a potential memory leak where in the
original code if write_ref_sha1() would fail we would end up returning from
the function without free()ing the msg string.

Note that this function is only called when fetching from a remote HTTP
repository onto the local (most of the time single-user) repository which
likely means that the type of collissions that the previous locking would
protect against and cause the fetch to fail for to be even more rare.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: make lock_ref_sha1 static

No external callers reference lock_ref_sha1 any more so lets declare it static.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: remove the update_ref_lock function

Since we now only call update_ref_lock with onerr==QUIET_ON_ERR we no longer
need this function and can replace it with just calling lock_any_ref_for_update
directly.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: remove the update_ref_write function

Since we only call update_ref_write from a single place and we only call it
with onerr==QUIET_ON_ERR we can just as well get rid of it and just call
write_ref_sha1 directly. This changes the return status for _commit from
1 to -1 on failures when writing to the ref. Eventually we will want
_commit to start returning more detailed error conditions than the current
simple success/failure. For example if the commit failed due to name
conflicts etc.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: remove lock_ref_sha1

lock_ref_sha1 was only called from one place in refc.c and only provided
a check that the refname was sane before adding back the initial "refs/"
part of the ref path name, the initial "refs/" that this caller had already
stripped off before calling lock_ref_sha1.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: make prune_ref use a transaction to delete the ref

Change prune_ref to delete the ref using a ref transaction. To do this we also
need to add a new flag REF_ISPRUNING that will tell the transaction that we
do not want to delete this ref from the packed refs. This flag is private to
refs.c and not exposed to external callers.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: make delete_ref use a transaction

Change delete_ref to use a ref transaction for the deletion. At the same time
since we no longer have any callers of repack_without_ref we can now delete
this function.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: pass the ref log message to _create/delete/update instead of _commit

Change the reference transactions so that we pass the reflog message
through to the create/delete/update function instead of the commit message.
This allows for individual messages for each change in a multi ref
transaction.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: pass NULL as *flags to read_ref_full

We call read_ref_full with a pointer to flags from rename_ref but since
we never actually use the returned flags we can just pass NULL here instead.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: pack all refs before we start to rename a ref

This means that most loose refs will no longer be present after the rename
which triggered a test failure since it assumes the file for an unrelated
ref would still be present after the rename.

We want to do this to make it easier to handle atomic renames in rename_ref for
the case 'git branch -m foo/bar foo'. If we can guarantee that foo/bar does not
exist as a loose ref we can avoid locking foo/bar.lock during transaction
commit and thus make it possible to delete the foo directory and re-create
it as a file(branch) in a single transaction.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: move the check for valid refname to lock_ref_sha1_basic

Move the check for check_refname_format from lock_any_ref_for_update
to lock_ref_sha1_basic. At some later stage we will get rid of
lock_any_ref_for_update completely.

This leaves lock_any_ref_for_updates as a no-op wrapper which could be removed.
But this wrapper is also called from an external caller and we will soon
make changes to the signature to lock_ref_sha1_basic that we do not want to
expose to that caller.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: call lock_ref_sha1_basic directly from commit

Skip using the lock_any_ref_for_update wrapper and call lock_ref_sha1_basic
directly from the commit function.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: pass a skip list to name_conflict_fn

Allow passing a list of refs to skip checking to name_conflict_fn.
There are some conditions where we want to allow a temporary conflict and skip
checking those refs. For example if we have a transaction that
1, guarantees that m is a packed refs and there is no loose ref for m
2, the transaction will delete m from the packed ref
3, the transaction will create conflicting m/m

For this case we want to be able to lock and create m/m since we know that the
conflict is only transient. I.e. the conflict will be automatically resolved
by the transaction when it deletes m.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
refs.c: propagate any errno==ENOTDIR from _commit back to the callers

In _commit, ENOTDIR can happen in the call to lock_ref_sha1_basic, either when
we lstat the new refname and it returns ENOTDIR or if the name checking
function reports that the same type of conflict happened. In both cases it
means that we can not create the new ref due to a name conflict.

For these cases, save the errno value and abort and make sure that the caller
can see errno==ENOTDIR.

Also start defining specific return codes for _commit, assign -1 as a generic
error and -2 as the error that refers to a name conflict. Callers can (and
should) use that return value inspecting errno directly.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>