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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.

install_exclusive.add_argument('-n', '--no-deps', dest='no_deps', action='store_true', default=False,
                                       help="Don't download {0}s listed as dependencies.".format(galaxy_type))
        install_exclusive.add_argument('--force-with-deps', dest='force_with_deps', action='store_true', default=False,
                                       help="Force overwriting an existing {0} and its "
                                            "dependencies.".format(galaxy_type))
        if galaxy_type == 'collection':
            install_parser.add_argument('-p', '--collections-path', dest='collections_path',
                                        default=C.COLLECTIONS_PATHS[0],
                                        help='The path to the directory containing your collections.')
            install_parser.add_argument('-r', '--requirements-file', dest='requirements',
                                        help='A file containing a list of collections to be installed.')
        else:
            install_parser.add_argument('-r', '--role-file', dest='role_file',
                                        help='A file containing a list of roles to be imported.')
            install_parser.add_argument('-g', '--keep-scm-meta', dest='keep_scm_meta', action='store_true',
                                        default=False,
                                        help='Use tar instead of the scm archive option when packaging the role.')
    def add_build_options(self, parser, parents=None):
        build_parser = parser.add_parser('build', parents=parents,
                                         help='Build an Ansible collection artifact that can be publish to Ansible '
                                              'Galaxy.')
        build_parser.set_defaults(func=self.execute_build)
        build_parser.add_argument('args', metavar='collection', nargs='*', default=('.',),
                                  help='Path to the collection(s) directory to build. This should be the directory '
                                       'that contains the galaxy.yml file. The default is the current working '
                                       'directory.')
        build_parser.add_argument('--output-path', dest='output_path', default='./',
                                  help='The path in which the collection is built to. The default is the current '
                                       'working directory.')
    def add_publish_options(self, parser, parents=None):