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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.

""" Setup an integration from Github or Travis for Ansible Galaxy roles"""
        if context.CLIARGS['setup_list']:
            
            secrets = self.api.list_secrets()
            if len(secrets) == 0:
                
                display.display("No integrations found.")
                return 0
            display.display(u'\n' + "ID         Source     Repo", color=C.COLOR_OK)
            display.display("---------- ---------- ----------", color=C.COLOR_OK)
            for secret in secrets:
                display.display("%-10s %-10s %s/%s" % (secret['id'], secret['source'], secret['github_user'],
                                                       secret['github_repo']), color=C.COLOR_OK)
            return 0
        if context.CLIARGS['remove_id']:
            
            self.api.remove_secret(context.CLIARGS['remove_id'])
            display.display("Secret removed. Integrations using this secret will not longer work.", color=C.COLOR_OK)
            return 0
        source = context.CLIARGS['source']
        github_user = context.CLIARGS['github_user']
        github_repo = context.CLIARGS['github_repo']
        secret = context.CLIARGS['secret']
        resp = self.api.add_secret(source, github_user, github_repo, secret)
        display.display("Added integration for %s %s/%s" % (resp['source'], resp['github_user'], resp['github_repo']))
        return 0
    def execute_delete(self):