Delete history before given commit, from local and remote repository

Question

Hi I have large repository with bunch of old commits for example:

A---B---...---L---M---N---O---P---Q
                       \     /
                        X---Y

I want to purge all commits before M. Is this posssible for local and remote repository, 
and How?

Thanks for proposals.

mfederowicz · Answer

I think I'll try shallow clone and then push to another repo and then replace repos if everything wil be ok

Balázs Szakmáry · Answer

If you create a shallow clone that starts at M and push this to another repo or force push it to the original one, that should do the job. Make sure you have a backup of all the branches before you start.