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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.

in_templates_dir = rel_root_dir == 'templates'
            dirs[:] = [d for d in dirs if not any(r.match(d) for r in skeleton_ignore_re)]
            for f in files:
                filename, ext = os.path.splitext(f)
                if any(r.match(os.path.join(rel_root, f)) for r in skeleton_ignore_re):
                    continue
                elif galaxy_type == 'collection' and own_skeleton and rel_root == '.' and f == 'galaxy.yml.j2':
                    
                    
                    
                    
                    template_data = inject_data.copy()
                    template_data['name'] = template_data.pop('collection_name')
                    meta_value = GalaxyCLI._get_skeleton_galaxy_yml(os.path.join(root, rel_root, f), template_data)
                    b_dest_file = to_bytes(os.path.join(obj_path, rel_root, filename), errors='surrogate_or_strict')
                    with open(b_dest_file, 'wb') as galaxy_obj:
                        galaxy_obj.write(to_bytes(meta_value, errors='surrogate_or_strict'))
                elif ext == ".j2" and not in_templates_dir:
                    src_template = os.path.join(rel_root, f)
                    dest_file = os.path.join(obj_path, rel_root, filename)
                    template_env.get_template(src_template).stream(inject_data).dump(dest_file, encoding='utf-8')
                else:
                    f_rel_path = os.path.relpath(os.path.join(root, f), obj_skeleton)
                    shutil.copyfile(os.path.join(root, f), os.path.join(obj_path, f_rel_path))
            for d in dirs:
                b_dir_path = to_bytes(os.path.join(obj_path, rel_root, d), errors='surrogate_or_strict')
                if not os.path.exists(b_dir_path):
                    os.makedirs(b_dir_path)
        display.display("- %s %s was created successfully" % (galaxy_type.title(), obj_name))
    def execute_info(self):