Optimize dvcignore

[karajan1001]

optimize #3869

• ❗ I have followed the Contributing to DVC checklist.

• 📖 If this PR requires documentation updates, I have created a separate PR (or issue, at least) in dvc.org and linked it here.

• ❌ I will check DeepSource, CodeClimate, and other sanity checks below. (We consider them recommendatory and don't expect everything to be addressed. Please fix things that actually improve code or fix bugs.)

Thank you for the contribution - we'll try to review it as soon as possible. 🙏

[efiop]

For the record: that strange bug with the number of calls of file_md5 was caused by #4244 . Please rebase and it will go away 🙂

[karajan1001]

  File "/opt/python/3.8.0/lib/python3.8/threading.py", line 890, in _bootstrap
    self._bootstrap_inner()
  File "/opt/python/3.8.0/lib/python3.8/threading.py", line 932, in _bootstrap_inner
    self.run()
  File "/opt/python/3.8.0/lib/python3.8/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/home/travis/virtualenv/python3.8.0/lib/python3.8/site-packages/mockssh/server.py", line 56, in handle_client
    command = self.command_queues[channel.chanid].get(block=True)
  File "/opt/python/3.8.0/lib/python3.8/queue.py", line 170, in get
    self.not_empty.wait()
  File "/opt/python/3.8.0/lib/python3.8/threading.py", line 302, in wait
    waiter.acquire()

what's this error?

[pared]

@karajan1001 when is it showing up? Running tests?

[karajan1001]

@pared
In (https://travis-ci.com/github/iterative/dvc/jobs/363240722)
After I fixed some typo error.

[pared]

@karajan1001
I restarted the build, seems fine now.

[karajan1001]

@pared

Excuse me, how can I restart build myself?
The network is unstable？

E           Exception: Command docker-compose -f "C:\Users\travis\build\iterative\dvc\tests\docker-compose.yml" -p "pytest-dvc-test" up --build -d returned 1: """Creating network "pytest-dvc-test_default" with the default driver
E           Pulling azurite (mcr.microsoft.com/azure-storage/azurite:3.3.0-preview)...
E           3.3.0-preview: Pulling from azure-storage/azurite
E           image operating system "linux" cannot be used on this platform
E           """.

[pared]

@karajan1001
You would need to have access to our builds. @efiop correct me if I am wrong but isn't it restricted to members of the organization?

[efiop]

test failures are unrelated. Thank you! 🙏