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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 Ansible collections to the path specified.
    :param collections: The collections to install, should be a list of tuples with (name, requirement, Galaxy server).
    :param output_path: The path to install the collections to.
    :param apis: A list of GalaxyAPIs to query when searching for a collection.
    :param validate_certs: Whether to validate the certificates if downloading a tarball.
    :param ignore_errors: Whether to ignore any errors when installing the collection.
    :param no_deps: Ignore any collection dependencies and only install the base requirements.
    :param force: Re-install a collection if it has already been installed.
    :param force_deps: Re-install a collection as well as its dependencies if they have already been installed.
    """
    existing_collections = _find_existing_collections(output_path)
    with _tempdir() as b_temp_path:
        display.display("Process install dependency map")
        with _display_progress():
            dependency_map = _build_dependency_map(collections, existing_collections, b_temp_path, apis,
                                                   validate_certs, force, force_deps, no_deps)
        display.display("Starting collection install process")
        with _display_progress():
            for collection in dependency_map.values():
                try:
                    collection.install(output_path, b_temp_path)
                except AnsibleError as err:
                    if ignore_errors:
                        display.warning("Failed to install collection %s but skipping due to --ignore-errors being set. "
                                        "Error: %s" % (to_text(collection), to_text(err)))
                    else:
                        raise
def validate_collection_name(name):