SHELL

remove git

rm -rf .git
-r => Remove directories and there contents recursively.
-f => Ignore nonexistent files and arguments, never prompt
for more info run 
rm --help

how to uninstall git

To remove just git package itself from Ubuntu 14.04 execute on terminal:
$ sudo apt-get remove git

To remove the git package and any other dependant package which are no longer needed from Ubuntu Trusty.
$ sudo apt-get remove --auto-remove git

Purging git
If you also want to delete configuration and/or data files of git from Ubuntu Trusty then this will work:
$ sudo apt-get purge git


To delete configuration and/or data files of git and it's dependencies from Ubuntu Trusty then execute:
$ sudo apt-get purge --auto-remove git

how to remove stuff from git

git rm -r File-Name