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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.

server_def = [('url', True), ('username', False), ('password', False), ('token', False),
                      ('auth_url', False)]
        config_servers = []
        for server_key in (C.GALAXY_SERVER_LIST or []):
            
            
            config_dict = dict((k, server_config_def(server_key, k, req)) for k, req in server_def)
            defs = AnsibleLoader(yaml.safe_dump(config_dict)).get_single_data()
            C.config.initialize_plugin_configuration_definitions('galaxy_server', server_key, defs)
            server_options = C.config.get_plugin_options('galaxy_server', server_key)
            
            
            auth_url = server_options.pop('auth_url', None)
            token_val = server_options['token'] or NoTokenSentinel
            username = server_options['username']
            
            server_options['token'] = None
            if username:
                server_options['token'] = BasicAuthToken(username,
                                                         server_options['password'])
            else:
                if token_val:
                    if auth_url:
                        server_options['token'] = KeycloakToken(access_token=token_val,
                                                                auth_url=auth_url,
                                                                validate_certs=not context.CLIARGS['ignore_certs'])
                    else:
                        
                        server_options['token'] = GalaxyToken(token=token_val)
            config_servers.append(GalaxyAPI(self.galaxy, server_key, **server_options))