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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.

publish_parser = parser.add_parser('publish', parents=parents,
                                           help='Publish a collection artifact to Ansible Galaxy.')
        publish_parser.set_defaults(func=self.execute_publish)
        publish_parser.add_argument('args', metavar='collection_path',
                                    help='The path to the collection tarball to publish.')
        publish_parser.add_argument('--no-wait', dest='wait', action='store_false', default=True,
                                    help="Don't wait for import validation results.")
        publish_parser.add_argument('--import-timeout', dest='import_timeout', type=int, default=0,
                                    help="The time to wait for the collection import process to finish.")
    def post_process_args(self, options):
        options = super(GalaxyCLI, self).post_process_args(options)
        display.verbosity = options.verbosity
        return options
    def run(self):
        super(GalaxyCLI, self).run()
        self.galaxy = Galaxy()
        def server_config_def(section, key, required):
            return {
                'description': 'The %s of the %s Galaxy server' % (key, section),
                'ini': [
                    {
                        'section': 'galaxy_server.%s' % section,
                        'key': key,
                    }
                ],
                'env': [
                    {'name': 'ANSIBLE_GALAXY_SERVER_%s_%s' % (section.upper(), key.upper())},
                ],
                'required': required,
            }