org-attach should detect git also higher in the filesystem

[Thomas Koch <thomas@koch.ro>]

Hi,

I tested org-attach with the org file being inside a git repo. I observed that 
the auto-commit feature of org-attach seems to work only if the data directory 
is the root of a git repo (detected by looking for a .git folder in the data 
folder).

I'd like however to have the org file in the git repo too and the data folder 
being a sub-folder of the git repo. Actually I'd also like to use git-annex 
here.

Some options of git rev-parse might be helpful here instead of coding the repo 
detection check by hand in elisp: 

--show-toplevel
           Show the absolute path of the top-level directory.

--is-inside-work-tree
           When the current working directory is inside the work tree of the 
repository print "true", otherwise "false".

What do you think?

Regards,

Thomas Koch, http://www.koch.ro