SVN
svn is version control software system that helps to maintain different version of a file may be a document or code file.
how to install
$ su
$ apt-get install subversion libapache2-svn
configure
$ mkdir /home/repo
$ cd /home/repo
$ svnadmin create test
$ chown -R www-data:subversion test
$ chmod -R g+rws myproject
$ svn co svn+ssh://localhost/home/amar/repo/test
$ svn status
$ svn add test.txt
$ svn commit -m ""
$ vim test.txt
$ svn status
$ svn log
$ svn log test.txt
$ svn up -r 2