.dockerignore ignores trailing slash on directories

[mikexstudios]

Since docker 1.4.0, .dockerignore files became .gitignore-like in that there is a difference between foo vs. foo/. The former can match files, symbolic links, etc. while the latter only matches the directory foo. This problem was also reported in: docker/compose#543.

Unfortunately, docker-py cannot handle foo/ syntax, and I suspect it's missing some other major cases. The reason is here:

docker-py/docker/utils/utils.py

Lines 67 to 68 in 0b78d7a

	def fnmatch_any(relpath, patterns):
	return any([fnmatch(relpath, pattern) for pattern in patterns])

. docker-py uses directories from os.walk which output directories without trailing slash and fnmatch can't match:

>>> from fnmatch import fnmatch
>>> fnmatch('src', 'src/')
False

My first thought was to suggest that docker-py use pathspec (https://github.com/cpburnz/python-path-specification) which implements .gitignore-style matching. However, I don't think the way that docker implements .dockerignore matching mirrors .gitignore-style matching (see: https://github.com/docker/docker/blob/master/pkg/fileutils/fileutils.go).

Does anyone have good ideas on an elegant fix?

As a temporary fix to anyone who stumbles on this issue, try to keep your .dockerignore file as simple as possible if you find that certain directories are not being ignored.

[shin-]

Hey @mikexstudios , thank you for reporting this!

I should have a patch for this by the end of the day, do you think you could help me test it with a real-life .dockerignore file?

[mikexstudios]

Hey @shin-. I updated your PR with a unit test for this case. Your PR works for detecting trailing slashes on folders.

However, I am concerned that we need a more general and robust way of handling .dockerignore files. The currently implementation fails on a lot of syntax defined here: https://github.com/docker/docker/blob/master/docs/sources/reference/builder.md#dockerignore-file

I'll see if I can contribute to improving this in docker-py.

[aanand]

Closed by #721.