Some old small changes to git-strings

Hi again,

Here is a small commit which cleaned up the git-strings code (it is old I just noticed it was never merged.) 

Also I see you are starting to write some documentation.   Can you give some pointers on how it is structured?   I see a few `*.rst` files, so I assume you are thinking of one `rst` file per "function group".   Is there, will there be, an overall index file? 

Also I see you are using sphinx.   I tried to run the `build` script in the doc directory, but 
it did not work.  (Obviously I do not have sphinx installed, and also not the command 
`virtualenv`.)  Do you have a pointer to a website where I can look on how to install the prerequisites?

Sorry for the many questions, 

Kind regards,
Wim Oudshoorn