Makefile: changed venv name
 source/conf.py: simplified themes stuff.
fixed indexing.

modified:
   source/deploy.rst
   source/error_fix.rst
   source/filter-branch.rst
   source/git_archive.rst
   source/git_info.rst
   source/merge.rst
fixed progit links

-   in hooks.rst, merge.rst, revparse.rst
source/revparse.rst: added index entries.