Re: purging unwanted history

> On 2008.11.17 03:24:12 +0100, Björn Steinbrink wrote:
>> On 2008.11.17 10:56:23 +1030, Geoff Russell wrote:
>> > I have a repository with 5 years worth of history, I only want to keep
>> > 1 year, so I want to purge the first 4 years. As it happens, the
>> > repository only has a single branch which should simplify the problem.
>>
>> Use filter-branch to drop the parents on the first commit you want to
>> keep, and then drop the old cruft.
>>
>> Let's say $drop is the hash of the latest commit you want to drop. To
>> keep things sane and simple, make sure the first commit you want to
>> keep, ie. the child of $drop, is not a merge commit. Then you can use:
>>
>> git filter-branch --parent-filter "sed -e 's/-p $drop//'" \
>>       --tag-name-filter cat -- \
>>       --all ^$drop
>>
>> The above rewrites the parents of all commits that come "after" $drop.
>>
>> Check the results with gitk.
>>
>>
>> Then, to clean out all the old cruft.
>>
>> First, the backup references from filter-branch:
>>
>> git for-each-ref --format='%(refname)' refs/original | \
>>       while read ref
>>       do
>>               git update-ref -d "$ref"
>>       done
>>
>> Then clean your reflogs:
>> git reflog expire --expire=0 --all
>>
>> And finally, repack and drop all the old unreachable objects:
>> git repack -ad
>> git prune # For objects that repack -ad might have left around
>>
>> At that point, everything leading up to and including $drop should be
>> gone.
>
> Hm, on second thought, if you have tags referencing some of the old
> history, they'll still be around, I think. Just delete those before you
> start the rewriting.
>
> And of course do the above with a copy of your repo. Just in case.
>
> Björn
>