github error: insufficient permission for adding an object to repository database

github error: insufficient permission for adding an object to repository
database

I used to be able to do, from my App folder:
git add .
git commit -m "commit details"
git push
and the latest version of my app on my local machine would be backed up on
in my master repo, on github.
Now, when I get as far as just the git add . command, I get:
mycompaq@ubuntu:~/myapp$ git add .
error: insufficient permission for adding an object to repository database
.git/objects
error: app/views/reviews/update.js.erb: failed to insert into database
error: unable to index file app/views/reviews/update.js.erb
fatal: updating files failed
mycompaq@ubuntu:~/myapp$
I read in a message on Stackoverflow the way to overcome a similar problem
was with:
chown -R user:user /project/directory
But seeing as I got in a whole load of trouble in the first place by
running commands I wasn't sure about, I want to know if this is the
command for me. What does it do? Can it be undone?
What should the exact syntax be, if the user is 'Christophe', and the
folder where my Rails app is stored is called 'myapp'. I mean should it be
chown -R user:christophe /myapp/app/views/reviews/update.js.erb
Sorry for all the questions.