Add full-file code browser - ie commit-tree viewer

[rtyley]

Agit currently gives commit-diffs as the only way to view file contents. A commit-tree viewer than lets you see all files in their state at that precise commit, view each file - and filter easily by name - would be great.

from Joel:

What I am missing is a real code browser. You can only take a look to the part
of files which got changed in a selected commit, but sometimes, when I'm in a
train for example, I'd really like to browse ALL the files from the repo in their
current state completley.

A workaround for the time being is to do a non-bare checkout and view the checked out files using a file-browser app- see

https://github.com/rtyley/agit/wiki/Bare-Repos https://github.com/rtyley/agit/wiki/Finding-Your-Files