GIT hacks

• fatal: in unpopulated submodule ‘x’

 git rm --cached x
 git submodule add -b master --force  https://gitlink/repo.git x

where x : the name of the submodule

• delete pushed commit on the remote branch

git reset --hard <last_working_commit_id
git push --force

• revert a change of speicifc file that is commited

git checkout commitId -- src/path/somefile