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author | Patrick Steinhardt <ps@pks.im> | 2020-04-02 09:10:02 +0200 |
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committer | Junio C Hamano <gitster@pobox.com> | 2020-04-02 11:09:49 -0700 |
commit | e48cf33b61b8fecf1558fb32fcf5ee2987e82890 (patch) | |
tree | 39e57596523fdf5bc71b71e6f047a4e0f9f9f642 /templates/hooks--fsmonitor-watchman.sample | |
parent | update-ref: read commands in a line-wise fashion (diff) | |
download | tgif-e48cf33b61b8fecf1558fb32fcf5ee2987e82890.tar.xz |
update-ref: implement interactive transaction handling
The git-update-ref(1) command can only handle queueing transactions
right now via its "--stdin" parameter, but there is no way for users to
handle the transaction itself in a more explicit way. E.g. in a
replicated scenario, one may imagine a coordinator that spawns
git-update-ref(1) for multiple repositories and only if all agree that
an update is possible will the coordinator send a commit. Such a
transactional session could look like
> start
< start: ok
> update refs/heads/master $OLD $NEW
> prepare
< prepare: ok
# All nodes have returned "ok"
> commit
< commit: ok
or
> start
< start: ok
> create refs/heads/master $OLD $NEW
> prepare
< fatal: cannot lock ref 'refs/heads/master': reference already exists
# On all other nodes:
> abort
< abort: ok
In order to allow for such transactional sessions, this commit
introduces four new commands for git-update-ref(1), which matches those
we have internally already with the exception of "start":
- start: start a new transaction
- prepare: prepare the transaction, that is try to lock all
references and verify their current value matches the
expected one
- commit: explicitly commit a session, that is update references to
match their new expected state
- abort: abort a session and roll back all changes
By design, git-update-ref(1) will commit as soon as standard input is
being closed. While fine in a non-transactional world, it is definitely
unexpected in a transactional world. Because of this, as soon as any of
the new transactional commands is used, the default will change to
aborting without an explicit "commit". To avoid a race between queueing
updates and the first "prepare" that starts a transaction, the "start"
command has been added to start an explicit transaction.
Add some tests to exercise this new functionality.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'templates/hooks--fsmonitor-watchman.sample')
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