git integration for contestants

[zielmicha]

Contestants would have an option to push (and pull) to https://harnas/git/contest/contest-name to automatically submit tasks. The repo structure would look like this:

/run.cpp
/foo.py

The language and problem ID would be parsed from file name. Push (post-receive) hook would submit problems and print URL of the status page.

remote: Counting objects: 11, done.
remote: Compressing objects: 100% (5/5), done.
remote: Total 7 (delta 2), reused 0 (delta 0)
Unpacking objects: 100% (7/7), done.
From https://harnas/git/contest/contest-name
 * branch            master     -> FETCH_HEAD
Updating 9d447d2..f74fb21
remote: Submitting task RUN (new version of file)
remote: Check status at: https://harnas/contest/foobar/status?task=run
remote: Submitting task FOO (new file)
remote: Check status at: https://harnas/contest/foobar/status?task=foo