##### SUMMARY
If you have executable files in your source code they are not kept in the tarball.

Could be related to https://github.com/ansible/ansible/blob/99d7f150873011e7515851db9b44ff486efa9d77/lib/ansible/galaxy/collection.py#L763

This was noticed as I had some auxiliary scripts in my repo.

Need to also consider scripts in `files/` if/when Collections support roles.

This seems to fail the "principal of least suprise"

**Proposal 1: Keep on stripping executable flags**

Add some line to the output
`WARNING: tests/coverage.sh: source file has executable flag, though this will be ignored in generated tar.gz`
Update developing a collection documentation page
Update integration tests to ensure that executable mode is always stripped.
Update code to link to this issue

**Proposal 2: Allow executible flags**

Update developing a collection documentation page
Update integration tests to ensure that executable mode is preserved
Update code to link to this issue
Changelog


##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
ansible-galaxy

##### ANSIBLE VERSION
```paste below
2.10
```

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

<!--- HINT: You can paste gist.github.com links for larger files -->


self._metadata = metadata
        self._files = files
        self.add_requirement(parent, requirement)
    def __str__(self):
        return to_native("%s.%s" % (self.namespace, self.name))
    def __unicode__(self):
        return u"%s.%s" % (self.namespace, self.name)
    @property
    def metadata(self):
        self._get_metadata()
        return self._metadata
    @property
    def versions(self):
        if self.allow_pre_releases:
            return self._versions
        return set(v for v in self._versions if v == '*' or not SemanticVersion(v).is_prerelease)
    @versions.setter
    def versions(self, value):
        self._versions = set(value)
    @property
    def pre_releases(self):
        return set(v for v in self._versions if SemanticVersion(v).is_prerelease)
    @property
    def latest_version(self):
        try:
            return max([v for v in self.versions if v != '*'], key=SemanticVersion)
        except ValueError:  
            return '*'
    @property
    def dependencies(self):