Move git tests all to one file.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Explicitly clean up temporary directories.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Explicitly specify encoding.

The default encoding is utf-8, which is what we want, but it's confusing
not to specify it.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>