Re: Trying to use git-filter-branch to compress history by removing large, obsolete binary files

[Andreas Ericsson <ae@op5.se>]

Dmitry Potapov wrote:
> On Sun, Oct 07, 2007 at 06:22:28PM -0600, Elijah Newren wrote:
>> git-filter-branch --tree-filter 'rm -f testme.txt' HEAD
>> git reset --hard
>> rm -rf .git/refs/original/
>> vi .git/packed-refs
>> # Use vi to remove the line referring to refs/original...
>> git reflog expire --all --expire-unreachable=0
>> git gc --prune
>>
>> Seems like a wrapper is needed.  :-)
> 
> Actually, I would rather not, because you rarely need to remove anything
> immediately, and 30 days delay is reasonable time to give you a chance
> to recover that you removed accidentally. You can reduce it by setting
> appropriate value for gc.reflogExpireUnreachable in your configuration.
> The only thing you need to do is to remove .git/refs/original/heads/something
> after you are sure that git-filter-branch did exactly what you wanted.
> 
>>> Warning: all unreachable references will be removed!
>> What other scenarios could lead to unreachable references?
> 
> Any re-writing of history leads to that.
> 

git-rebase being the most common culprit, right alongside 'git commit --amend'.

>> I don't
>> know how to determine whether this is safe or not (except that these
>> were test repositories anyway, so I don't care what happens to them).
> 
> Git logs all your action, so even re-writing history would not be
> so disastrous if you suddenly realized that you did something wrong.
> The history is stored for 30 days by default. Usually, you do not
> need to mess with Git internals like you did above. Your useless
> files still will disappear after being unreachable for 30 days.
> 
> OTOH, if you want to have a clean repository immediately, I believe
> 'git clone' is a better option. After you made a local clone using
> it, 'git gc' should remove old garbage.
> 

A clone only fetches revs reachable from a ref, so pruning immediately
after a clone is completely pointless.

-- 
Andreas Ericsson                   andreas.ericsson@op5.se
OP5 AB                             www.op5.se
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