From: Steffen Prohaska <prohaska@zib.de>
Date: Wed, 04 Jul 2007 13:27:24 GMT
Subject: Re: efficient way to filter several branches with common history?
Message-ID: <6DC0E50A-CAD3-453E-BD9C-73E51EDD5785@zib.de>
In-Reply-To: <468B5C4B.26F5E90B@eudaptics.com>


On Jul 4, 2007, at 10:37 AM, Johannes Sixt wrote:

> Steffen Prohaska wrote:
>>
>> Is there an efficient way to filter several branches at once
>> through git-filter-branch? Often several branches have a lot
>> of common history. Therefore, I suspect it would be much more
>> efficient to filter them with one call to git-filter-branch.
>> For example how can I efficiently filter all origin/* branches
>> to filtered/* branches?
>
> That feature is not yet implemented.
>
> In the meantime do it this way:
>
> Make an octopus merge of the branches onto a new branch. (If you have
> more than a dozen or so, you better make a hierarchy of  
> octopusses.) You
> don't need to resolve conflicts (you are not interested in the merge
> result), or use -s ours to avoid them in the first place.
> Then filter that new branch.
> Then create new refs at the rewritten commits:
>
>    $ git update-ref refs/filtered/b1 $id-of-rewritten-origin/b1
>    $ ...
>
> Use gitk to find the $ids-of-rewritten-origin/*

Thanks for your explanation. The following is the template I used
to build my fully automated version of what you proposed:

--- SNIP ---
echo "merging branches to be filtered ..."
git-checkout -b tmp/all origin/master

for b in origin/branchX origin/branchY [ ... more branches here ...]
do
     git merge -s ours -m "merge-for-preparing-filter-branch $b" $b
done

echo "... filtering ..."
git-filter-branch \
[... your git-filter-branch filters here ...] \
   filtered/all >filter-branch.log

echo "... setting heads of filtered branches."
lastp1=
git-log --pretty="format:%s %P" filtered/all |
while read t b p1 p2
do
     [[ "$t" == "merge-for-preparing-filter-branch" ]] || { git  
update-ref refs/heads/filtered/master $lastp1 ; break ; }
     b=filtered/$(basename $b)
     git update-ref refs/heads/$b $p2
     lastp1=$p1
done

echo "delete tmp/all and filtered/all after checking the result"
--- SNIP ---

	Steffen