I have git repository with many, many (2000+) commits, for example:
l-- m -- n
/
a -- b -- c -- d -- e -- f -- g -- h -- i -- j -- k
\
x -- y -- z
and I want to truncate old log history - delete all commits from log history starting from (for example) commit "f" but as the beginning of repository.
How to do it?
In order not to lose some history; better first take a copy of your repository :). Here we go: (<f> is the sha of the commit f that you want to be the new root commit)
git checkout --orphan temp <f> # checkout to the status of the git repo at commit f; creating a branch named "temp"
git commit -m "new root commit" # create a new commit that is to be the new root commit
git rebase --onto temp <f> master # now rebase the part of history from <f> to master onthe temp branch
git branch -D temp # we don't need the temp branch anymore
If you have a remote where you want to have the same truncated history; you can use git push -f. Warning this is a dangerous command; don't use this lightly! If you want to be sure that your last version of the code is still the same; you can run git diff origin/master. That should show no changes (since only the history changed; not the content of your files).
git push -f
The following 2 commands are optional - they keep your git repo in good shape.
git prune --progress # delete all the objects w/o references
git gc --aggressive # aggressively collect garbage; may take a lot of time on large repos