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##### SUMMARY
The "source" folder of my collection contains several files that are not directly related to the collection itself. E.g. a `.gitignore`, a `.github` folder, a `Makefile` etc.
When using `ansible-galaxy collection build <folder>`, these files are included in the generated tarball. This is especially hurtful when the source folder also contains a Python venv that I use for developing.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
ansible-galaxy

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.9.0.dev0
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/home/egolov/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /home/egolov/Devel/ansible/ansible/lib/ansible
  executable location = /home/egolov/Devel/ansible/ansible/bin/ansible
  python version = 2.7.15 (default, Oct 15 2018, 15:26:09) [GCC 8.2.1 20180801 (Red Hat 8.2.1-2)]

```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
empty
```

##### OS / ENVIRONMENT
Fedora


##### STEPS TO REPRODUCE
Build a collection :)

##### EXPECTED RESULTS
I'd expect only collection-relevant files/folders (those that are listed in the spec/docs) to be included.


##### ADDITIONAL INFORMATION
Alternatively, a ignore file as suggested by @bcoca  in https://github.com/ansible/ansible/pull/59121/files#r304554334 could be a fix for this.

data.append(format_str % (u"Name", u"Description"))
        data.append(format_str % (u"----", u"-----------"))
        for role in response['results']:
            data.append(format_str % (u'%s.%s' % (role['username'], role['name']), role['description']))
        data = u'\n'.join(data)
        self.pager(data)
        return True
    def execute_login(self):
        """
        verify user's identify via Github and retrieve an auth token from Ansible Galaxy.
        """
        
        if context.CLIARGS['token'] is None:
            if C.GALAXY_TOKEN:
                github_token = C.GALAXY_TOKEN
            else:
                login = GalaxyLogin(self.galaxy)
                github_token = login.create_github_token()
        else:
            github_token = context.CLIARGS['token']
        galaxy_response = self.api.authenticate(github_token)
        if context.CLIARGS['token'] is None and C.GALAXY_TOKEN is None:
            
            login.remove_github_token()
        
        token = GalaxyToken()
        token.set(galaxy_response['token'])
        display.display("Successfully logged into Galaxy as %s" % galaxy_response['username'])
        return 0
    def execute_import(self):