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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.

if "include" not in requirement:
                role = RoleRequirement.role_yaml_parse(requirement)
                display.vvv("found role %s in yaml file" % to_text(role))
                if "name" not in role and "src" not in role:
                    raise AnsibleError("Must specify name or src for role")
                return [GalaxyRole(self.galaxy, self.api, **role)]
            else:
                b_include_path = to_bytes(requirement["include"], errors="surrogate_or_strict")
                if not os.path.isfile(b_include_path):
                    raise AnsibleError("Failed to find include requirements file '%s' in '%s'"
                                       % (to_native(b_include_path), to_native(requirements_file)))
                with open(b_include_path, 'rb') as f_include:
                    try:
                        return [GalaxyRole(self.galaxy, self.api, **r) for r in
                                (RoleRequirement.role_yaml_parse(i) for i in yaml.safe_load(f_include))]
                    except Exception as e:
                        raise AnsibleError("Unable to load data from include requirements file: %s %s"
                                           % (to_native(requirements_file), to_native(e)))
        if isinstance(file_requirements, list):
            
            if not allow_old_format: