space chars at start of .gitignore

[gtors]

If .gitignore starts with 20 20 0a (in hex), then dulwich will read it as Pattern(b"", False)

So, this cause some strange bug for me, for example my dir app/web become ignorable, but in reality it is not.

In my case, dulwich was used as dependency of DVC tool (https://github.com/iterative/dvc/blob/7700d555296e52564dd27d767406104c994e42c1/dvc/scm/git/backend/dulwich.py#L281)

Seems, that function doesn't handle situation than line contains only space chars https://github.com/dulwich/dulwich/blob/76dd8356f9d8870f44226e4232c24fbc1e573e93/dulwich/ignore.py#L114-L140

[gtors]

line = b"  \n"
line.rstrip(b"\r\n") 

line will be b" " here

[jelmer]

Any chance you can add a test case for this to dulwich/tests/test_ignore.py ? that should be fairly straightforward to do; a proper fix would also be great, but I'm also happy to take it from there.

[gtors]

Ok, I will try.