Re: [PATCH v0] fast-import: Add drop command

> On Sat, Sep 24, 2011 at 10:19 PM, Dmitry Ivankov <divanorama@gmail.com> wrote:
>> On Sun, Sep 25, 2011 at 1:37 AM, Jonathan Nieder <jrnieder@gmail.com> wrote:
>>> Thanks.  I must have missed the earlier discussion.  What are the
>>> semantics of this command and its intended purpose?
>> My guess is that if fast-import is used to manage a set of "remote"
>> branches, it should be able to delete branches. Then, it should
>> be allowed to do non-fastforward updates too (--force). Why can't
>> it just ignore branches deletion (considering --force)?
>
> I started by using --force, but I did not want to completely disable
> these checks. The idea of the drop command is to add support to the
> exceptions that require non-fastforward updates.
>
>> Random thoughts:
>> 1. once 'drop' is executed, fast-import can't tell if the branch was
>> actually deleted. And moreover any attempt to read this branch
>> head becomes illegal (either it's missing in .git or fast-import is
>> instructed to use a dropped branch).
>> 2. 'reset' command is a bit like proposed 'drop' but it never deletes
>> a branch ref. Consider following imports:
>> 1) import branch topic
>> 2) reset topic
>> 3) import branch topic2 starting at topic (incorrect import)
>> If 1-3) is done in one fast-import process, the error is reported.
>> If 3) is done separately, it succeeds but the result is strange:
>> topic2 isn't started from scratch but from old "erased" topic.
>> So, maybe, reset should be fixed to erase branches on --force.
>
> I think you are not considering the possibility that checkpoints could
> have been done along the way. I use them frequently to be able to
> analyse branches with diff-tree. As soon as a checkpoint is done,
> update-branches will issue an error (commit A is not part of branch A').
>
>> One more scenario is:
>> 1) import topic
>> 2) reset topic
>> 3) import topic
>> If 1-3) go together - no error
>> If 3) goes separate - no error, but non-fastforward update.
>> Much more harmless, but still may look strange.
>
> Not exactly true if there is a checkpoint done after step 1.
>
> My scenario is:
>
> 1) import topic
> 2) checkpoint
> 3) diff-tree and processing
> 4) exit if processing returns ok
> 5) reset topic to another HEAD
> 6) goto 1)