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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.

for name, version, source in collections:
        _get_collection_info(dependency_map, existing_collections, name, version, source, b_temp_path, apis,
                             validate_certs, (force or force_deps))
    checked_parents = set([to_text(c) for c in dependency_map.values() if c.skip])
    while len(dependency_map) != len(checked_parents):
        while not no_deps:  
            parents_to_check = set(dependency_map.keys()).difference(checked_parents)
            deps_exhausted = True
            for parent in parents_to_check:
                parent_info = dependency_map[parent]
                if parent_info.dependencies:
                    deps_exhausted = False
                    for dep_name, dep_requirement in parent_info.dependencies.items():
                        _get_collection_info(dependency_map, existing_collections, dep_name, dep_requirement,
                                             parent_info.api, b_temp_path, apis, validate_certs, force_deps,
                                             parent=parent)
                    checked_parents.add(parent)
            
            if deps_exhausted:
                break
        
        
        deps_not_checked = set(dependency_map.keys()).difference(checked_parents)
        for collection in deps_not_checked:
            dependency_map[collection].set_latest_version()
            if no_deps or len(dependency_map[collection].dependencies) == 0:
                checked_parents.add(collection)
    return dependency_map
def _get_collection_info(dep_map, existing_collections, collection, requirement, source, b_temp_path, apis,