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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.

roles_left.append(dep_role)
                                else:
                                    display.warning('- dependency %s (%s) from role %s differs from already installed version (%s), skipping' %
                                                    (to_text(dep_role), dep_role.version, role.name, dep_role.install_info['version']))
                            else:
                                if force_deps:
                                    roles_left.append(dep_role)
                                else:
                                    display.display('- dependency %s is already installed, skipping.' % dep_role.name)
            if not installed:
                display.warning("- %s was NOT installed successfully." % role.name)
                self.exit_without_ignore()
        return 0
    def execute_remove(self):
        """
        removes the list of roles passed as arguments from the local system.
        """
        if not context.CLIARGS['args']:
            raise AnsibleOptionsError('- you must specify at least one role to remove.')
        for role_name in context.CLIARGS['args']:
            role = GalaxyRole(self.galaxy, self.api, role_name)
            try:
                if role.remove():
                    display.display('- successfully removed %s' % role_name)
                else:
                    display.display('- %s is not installed, skipping.' % role_name)
            except Exception as e:
                raise AnsibleError("Failed to remove role %s: %s" % (role_name, to_native(e)))
        return 0
    def execute_list(self):