Re: [PATCH 0/3] merge -Xindex-only

[Michael Haggerty <mhagger@alum.mit.edu>]

On 07/08/2013 05:44 PM, Thomas Rast wrote:
> Michael Haggerty <mhagger@alum.mit.edu> writes:
> 
>> [Resend because of address confusion in replied-to email.]
>>
>> On 07/07/2013 08:00 PM, Thomas Rast wrote:
>>> I recently looked into making merge-recursive more useful as a modular
>>> piece in various tasks, e.g. Michael's git-imerge and the experiments
>>> I made in showing evil merges.
>>>
>>> This miniseries is the extremely low-hanging fruit.  If it makes a
>>> good first step for git-imerge, perhaps it can go in like this.  It's
>>> not a big speedup (about 2.2s vs 2.4s in a sample conflicting merge in
>>> git.git), but it does feel much cleaner to avoid touching the worktree
>>> unless actually necessary.
>>>
>>> Otherwise it's probably not worth it just yet; for what I want to do
>>> with it, we need some more reshuffling of things.
>>
>> Interesting.
>>
>> For git-imerge, it would be nice to speed up merges by skipping the
>> working tree updates.  10% might not be so noticeable, but every little
>> bit helps :-)
>>
>> But the killer benefit would be if git-imerge could do some of its
>> automatic merge-testing and autofilling in the background while the user
>> is resolving conflicts in the main index and working tree.
>>
>> Is it possible to use this option with an alternate index file (e.g.,
>> via the GIT_INDEX_FILE environment variable)?  Can it be made to leave
>> other shared state (e.g., MERGE_HEAD) alone?  If so, maybe it's already
>> there.
> 
> GIT_INDEX_FILE yes, that one works out of the box.
> 
> I think for the shared state, the following is a (probably) ridiculously
> unsupported yet magic way of achieving this:
> 
>   mkdir -p unshared/.git
>   cd unshared/.git
>   for f in ../../.git/*; do
>     case "$f" in
>       *HEAD | index)
>         cp "$f" .
>         ;;
>       *)
>         ln -s "$f" .
>         ;;
>     esac
>   done
> 
> That gives you a repository that propagates ref changes and object
> writing, but does not propagate changes to index, HEAD, FETCH_HEAD or
> MERGE_HEAD.  Which might just be what you need?
> 
> Note that as far as I'm concerned, this is a live handgrenade.  It could
> blow up in your face at any time, but it probably has its applications...

I might consider such a thing for my own use, but I don't think I'll lob
live hand grenades at innocent git-imerge users :-)

Since you've already implemented a way to merge into the index (even an
alternative index) without touching the working copy, I'll just cross my
fingers and hope for the appearance of an option that makes merge leave
HEAD, MERGE_HEAD, etc. untouched.

It's not like I have any free time to work on git-imerge anyway :-(

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/