garbage_collecting.rst: minor format fix.
source/merge.rst: minor format fix.
source/subtree.rst: clarified.
source/conf.py: added automatic release from git.
git_info.rst: reordered and added material.
Makefile: changed sphinxbuild to use a virtualenv.
source/subtree.rst: more content, +commit graphs.
source/merge.rst: added "keeping one branch"
source/garbage_collecting.rst: more content.
source/conf.py: changed highlight_language, added graphviz ext.
Makefile: + xml targets and security check for sphinx-build
source/error_fix.rst: more on rebase interactive
source/filter-branch.rst: more content, added repo cleaning, and indexes
* source/git_info.rst: added difftool.
git_info.rst: updated "git grep" examples.
git-info.rst: rewording and added top-level section.
rebase.rst: began new section on rebase and added to index.rst
remote.rst: more content on remotes.
conf.py: new content

     added rtd option,
     added themes,
     git versioning,
     merged with current sphinx default
.dir-locals.el: added orglink-mode for notes