From: Junio C Hamano <gitster@pobox.com>
To: Johannes Sixt <j6t@kdbg.org>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 7/7] push: document --lockref
Date: Sat, 13 Jul 2013 13:08:09 -0700 [thread overview]
Message-ID: <7vr4f2gr4m.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <7vwqougwec.fsf@alter.siamese.dyndns.org> (Junio C. Hamano's message of "Sat, 13 Jul 2013 11:14:19 -0700")
Junio C Hamano <gitster@pobox.com> writes:
> If "--lockref" automatically implies "--allow-no-ff" (the design in
> the reposted patch), you cannot express that combination. But once
> you use "--lockref" in such a situation , for the push to succeed,
> you know that the push replaces not just _any_ ancestor of what you
> are pushing, but replaces the exact current value. So I do not think
> your implicit introduction of --allow-no-ff via redefining the
> semantics of the plus prefix is not adding much value (if any),
> while making the common case less easy to use.
>
>> No; --lockref only adds the check that the destination is at the
>> expected revision, but does *NOT* override the no-ff check.
>
> You _could_ do it in that way, but that is less useful.
Another issue I have with the proposal is that we close the door to
"force only this one" convenience we have with "+ref" vs "--force
ref". Assuming that it is useful to require lockref while still
making sure that the usual "must fast-forward" rule is followed (if
that is not the case, I do not see a reason why your proposal is any
useful---am I missing something?), I would prefer to allow users a
way to decorate this basic syntax to say:
git push --lockref master jch pu
things like
(1) pu may not fast-forward and please override that "must
fast-forward" check from it, while still keeping the lockref
safety (e.g. "+pu" that does not --force, which is your
proposal);
(2) any of them may not fast-forward and please override that "must
fast-forward" check from it, while still keeping the lockref
safety (without adding "--allow-no-ff", I do not see how it is
possible with your proposal, short of forcing user to add "+"
everywhere);
(3) I know jch does not fast-forward so please override the "must
fast-forward", but still apply the lockref safety, pu may not
even satisfy lockref safety so please force it (as the "only
force this one" semantics is removed from "+", I do not see how
it is possible with your proposal).
So I would understand if your proposal _were_ to
* add "--allow-no-ff" option;
* change the meaning of "+ref" to "--allow-no-ff for only this
ref"; and
* add a new "*ref" (or whatever new syntax) to still allow people
to say "--force only this ref".
but we still need to assume that it makes sense to ask lockref but
still want to ensure the update fast-forwards. I personally do not
think it does [*1*].
The semantics the posted patch (rerolled to allow "--force" push
anything) implements lets "--lockref" to imply "--allow-no-ff" and
that makes it much simpler; we do not have to deal with any of the
above complexity.
[Footnote]
*1* The assurance --lockref gives is a lot stronger than "must
fast-forward". You may have fetched the topic whose tip was at
commit X, and rebased it on top of X~4 to create a new history
leading to Y.
o----o----Y
/
o---o----o----o----o----X
X~4
When you "git push --lockref=topic:X Y:X", you are requiring
their tip to be still at X. Other people's change cannot be to
add something on top of X (which will be lost if we replace the
tip of the topic with Y).
If your change were not a rebase but to build one of you own:
o---o----o----o----o----X---Y
your "git push --lockref=topic:X Y:X" still requires the tip is
at X. If somebody rewound the tip to X~2 in the meantime
(because they decided the tip 2 commits were not good), your
"git push Y:X" without the "--lockref" will lose their rewind,
because Y will still be a fast-forward update of X~2.
"--lockref=topic:X" will protect you in this case as well.
So I think "--lockref" that automatically disables "must
fast-forward" check is the right thing to do, as we are
replacing the weaker "must fast-forward" with something
stronger. I do not think we are getting anything from forcing
the user to say "--allow-no-ff" with "+ref" syntax when the
user says "--lockref". It is not making it safer, and it is
making it less convenient.
next prev parent reply other threads:[~2013-07-13 20:08 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-02 20:57 [RFD] Making "git push [--force/--delete]" safer? Junio C Hamano
2013-07-02 22:55 ` Johan Herland
2013-07-03 6:34 ` Johan Herland
2013-07-03 8:49 ` Junio C Hamano
2013-07-03 10:00 ` Johan Herland
2013-07-03 10:06 ` Jonathan del Strother
2013-07-03 10:11 ` Johan Herland
2013-07-03 10:50 ` Michael Haggerty
2013-07-03 12:06 ` Johannes Sixt
2013-07-03 19:53 ` Junio C Hamano
2013-07-04 5:37 ` Johannes Sixt
2013-07-04 5:46 ` Junio C Hamano
2013-07-03 19:50 ` Junio C Hamano
2013-07-03 20:18 ` Junio C Hamano
2013-07-03 19:48 ` Junio C Hamano
2013-07-09 19:53 ` [PATCH 0/7] safer "push --force" with compare-and-swap Junio C Hamano
2013-07-09 19:53 ` [PATCH 1/7] cache.h: move remote/connect API out of it Junio C Hamano
2013-07-09 19:53 ` [PATCH 2/7] builtin/push.c: use OPT_BOOL, not OPT_BOOLEAN Junio C Hamano
2013-07-09 19:53 ` [PATCH 3/7] push: beginning of compare-and-swap "force/delete safety" Junio C Hamano
2013-07-09 19:53 ` [PATCH 4/7] remote.c: add command line option parser for --lockref Junio C Hamano
2013-07-16 22:13 ` John Keeping
2013-07-17 17:06 ` Junio C Hamano
2013-07-17 17:09 ` Junio C Hamano
2013-07-09 19:53 ` [PATCH 5/7] push --lockref: implement logic to populate old_sha1_expect[] Junio C Hamano
2013-07-09 19:53 ` [PATCH 6/7] t5533: test "push --lockref" Junio C Hamano
2013-07-09 19:53 ` [PATCH 7/7] push: document --lockref Junio C Hamano
2013-07-09 20:17 ` Aaron Schrab
2013-07-09 20:39 ` Junio C Hamano
2013-07-09 20:24 ` Johannes Sixt
2013-07-09 20:37 ` Junio C Hamano
2013-07-09 20:55 ` Johannes Sixt
2013-07-09 22:09 ` Junio C Hamano
2013-07-09 23:08 ` Junio C Hamano
2013-07-11 21:10 ` Johannes Sixt
2013-07-11 21:57 ` Junio C Hamano
2013-07-11 22:14 ` Junio C Hamano
2013-07-12 17:21 ` Johannes Sixt
2013-07-12 17:40 ` Junio C Hamano
2013-07-12 20:00 ` Johannes Sixt
2013-07-12 21:19 ` Junio C Hamano
2013-07-13 6:52 ` Johannes Sixt
2013-07-13 18:14 ` Junio C Hamano
2013-07-13 20:08 ` Junio C Hamano [this message]
2013-07-13 21:11 ` Johannes Sixt
2013-07-14 14:28 ` John Keeping
2013-07-13 20:17 ` Johannes Sixt
2013-07-14 19:17 ` Junio C Hamano
2013-07-14 20:21 ` Johannes Sixt
2013-07-14 20:34 ` Jonathan Nieder
2013-07-14 20:49 ` Jonathan Nieder
2013-07-14 20:59 ` Johannes Sixt
2013-07-14 21:28 ` Jonathan Nieder
2013-07-15 4:10 ` Junio C Hamano
2013-07-15 4:44 ` Jonathan Nieder
2013-07-15 15:37 ` Junio C Hamano
2013-07-15 20:30 ` Johannes Sixt
2013-07-15 3:50 ` Junio C Hamano
2013-07-15 15:47 ` Default expectation of --lockref Junio C Hamano
2013-07-15 20:27 ` [PATCH 7/7] push: document --lockref Johannes Sixt
2013-07-09 21:37 ` Marc Branchaud
2013-07-09 20:27 ` Michael Haggerty
2013-07-09 20:42 ` Junio C Hamano
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