Subject: Re: squash commits deep down in history

From: Jakub Narębski <[email-masked]>
Date: Fri, 24 Oct 2014 13:43:22 +0200

W dniu 2014-10-23 22:08, Johannes Sixt pisze:
> Am 23.10.2014 um 14:34 schrieb Henning Moll:

>> i need to squash several commits into a single one in a automated
>> way. I know that there is interactive rebase, which can also be
>> automated using GIT_SEQUENCE_EDITOR. Unfortunately my history is very
>> large and i need to squash deep down in the history several times. So
>> using interactive rebase seems not to be the right tool.
>>
>> I wonder if i can solve this task using filter-branch? I have a file
>> that list the SHA1s for each squash operation per line. All SHA1s of
>> a line are in chronological order (youngest to oldest), or in other
>> words: the first SHA1 is the child of the second, and so on.
>
> Use git-replace do construct a squashed commit that replaces the last
> child in each run such that its parent points to the parent of the first
> in the run. Then use a git-filter-branch without filters to burn the
> parenthood into the history.

Using grafts (which are only about parentage, and are purely local) with 
filter-less git-filter-branch might be easier than git-replace.

If you have the following history:

     ... <--- O <--- A <--- B <--- C <--- ...

and you want to squash A, B, C into

     ... <--- O <----------------- C <--- ...

simply add the following to .git/info/grafts

    <sha-1 of C> <sha-1 of O>

for example with

    echo "$(git rev-parse C) $(git rev-parse C^^^)" >>.git/info/grafts

Check if the history is correct e.g. with "git log --graph --oneline",
then use filter-branch.

BTW. do you know if it is possible to run filter-branch without 
replacing replaces?

Just for completeness, yet another way to do scripted history rewriting 
is to use git-fast-export + some editing script (e.g. reposurgeon[1]) + 
git-fast-import.

[1]: http://www.catb.org/esr/reposurgeon/

-- 
Jakub Narębski