Dulwich performance workarounds

[jonashaag]

From #257, @jelmer, see

klaus/klaus/repo.py

Line 172 in 0fa6ab4

output = subprocess.check_output(cmd, cwd=os.path.abspath(self.path))

,

klaus/klaus/repo.py

Line 181 in 0fa6ab4

cmd = ['git', 'blame', '-ls', '--root', decode_from_git(commit.id), '--', path]

I don't have up-to-date speed comparisons of these but when I initially wrote the code, Dulwich was an order of magnitude slower.

[jelmer]

Thanks, I'll have a look. These are both operations that scale with the length of history per file.