refs.c: add transaction support for renaming a reflog

Add a new transaction function transaction_rename_reflog.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: update rename_ref to use a transaction

Change refs.c to use a single transaction to perform the rename.
Change the function to return 1 on failure instead of either -1 or 1.

These changes make the rename_ref operation atomic.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: rollback the lockfile before we die() in repack_without_refs

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: move reflog updates into its own function

write_ref_sha1 tries to update the reflog while updating the ref.
Move these reflog changes out into its own function so that we can do the
same thing if we write a sha1 ref differently, for example by writing a ref
to the packed refs file instead.

No functional changes intended. We only move some code out into a separate
function.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: write updates to packed refs when a transaction has more than one ref

When we are updating more than one single ref, i.e. not a commit, then
write the updated refs directly to the packed refs file instead of writing
them as loose refs.

Change clone to use a transaction instead of using the packed refs API.
This changes the behavior of clone slightly. Previously clone would always
clone all refs into a packed refs file. With this change clone will only
clone into packed refs iff there are two or more refs being cloned.
If the repository we are cloning from only contains exactly one single ref
then clone will now store this as a loose ref. The benefit here is that
we no longer need to export a bunch of API functions to clone to access
packed refs directly. Clone can now just use a normal transaction and all
the packed refs goodness will happen automatically.

Update the t5516 test to cope with the fact that clone now only uses
packed refs if there are more than one ref being cloned.

We still use loose refs for single ref transactions, such as are used
by 'git commit' and friends. The reason for this is that if you have very
many refs then having to re-write the whole packed refs file for every
common operation like commit would have a performance impact.
That said, with these changes it should now be fairly straightforward to
add support to optionally start using packed refs for ALL updates
which could solve existing issues with name clashes in case insensitive
filesystems.

This change also means that multi-ref updates will now appear as a single
atomic change to any external observers instead of a sequence of discreete
changes.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
remote.c: use a transaction for deleting refs

Transactions now use packed refs when deleting multiple refs so there is no
need to do it manually from remote.c any more.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: make repack_without_refs static

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: make the *_packed_refs functions static

We no longer need to expose the lock/add/commit/rollback functions
for packed refs anymore so make them static and remove them from the
public api.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: replace the onerr argument in update_ref with a strbuf err

Get rid of the action_on_err enum and replace the action argument to
update_ref with a strbuf *err for error reporting.

Update all callers to the new api including two callers in transport*.c
which used the literal 0 instead of an enum.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: make add_packed_ref return an error instead of calling die

Change add_packed_ref to return an error instead of calling die().
Update all callers to check the return value of add_packed_ref.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: make lock_packed_refs take an err argument

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
refs.c: add an err argument to pack_refs

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>