Remove `Repo` hack from model.py

[SeanBryan51]

On this line:

benchcab/benchcab/model.py

Lines 40 to 41 in 6f586a1

	if isinstance(repo, GitRepo):
	self.src_dir = Path("src")

The Model class should not have to know whether repo is a GitRepo or an SVNRepo, we should only be working with the Repo interface. This should be addressed if we want to properly test the model and repo modules.

Originally posted by @SeanBryan51 in #208 (comment)

[ccarouge]

I wonder if we could use something like Path.rglob() to find the path to the offline/ directory instead of hard-wiring it. I haven't checked if we use Model.src_dir for anything else.

[ccarouge]

I also think this should be changed:

benchcab/benchcab/model.py

Line 107 in 6f586a1

path_to_repo = self.root_dir / internal.SRC_DIR / self.name

It should probably be given by the repo instead of set in Model.