<!--- Verify first that your issue is not already reported on GitHub -->
<!--- Also test if the latest release and devel branch are affected too -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### SUMMARY
<!--- Explain the problem briefly below -->
We publish semver collection (vyos.vyos:0.0.1-dev58) to ansible galaxy, however by default it seems ansible-galaxy client will not be able to find it. You must specific the version number directly to fetch it.

https://galaxy.ansible.com/vyos/vyos


EDIT:

This is working as expect, but it would be nice to Include:

   --pre                       Include pre-release and development versions. By default, ansible-galaxy only finds stable versions.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
ansible-galaxy

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.9.1
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```


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

<!--- Paste example playbooks or commands between quotes below -->
```yaml
$ ansible-galaxy collection install vyos.vyos -p /tmp/11123
[WARNING]: The specified collections path '/tmp/11123' is not part of the configured Ansible collections paths '/home/pabelanger/.ansible/collections:/usr/share/ansible/collections'. The
installed collection won't be picked up in an Ansible run.

Process install dependency map
ERROR! Cannot meet requirement * for dependency vyos.vyos from source 'https://galaxy.ansible.com/api/'. Available versions before last requirement added: 
Requirements from:
	base - 'vyos.vyos:*'
(venv) [pabelanger@localhost openstack]$ ansible-galaxy collection install vyos.vyos:0.0.1-dev57 -p /tmp/11123
[WARNING]: The specified collections path '/tmp/11123' is not part of the configured Ansible collections paths '/home/pabelanger/.ansible/collections:/usr/share/ansible/collections'. The
installed collection won't be picked up in an Ansible run.

Process install dependency map
Starting collection install process
Installing 'vyos.vyos:0.0.1-dev57' to '/tmp/11123/ansible_collections/vyos/vyos'
```

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

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
vyos.vyos collection to be found and installed

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below

```

rel_path = to_text(b_rel_path, errors='surrogate_or_strict')
            if os.path.isdir(b_abs_path):
                if any(b_item == b_path for b_path in b_ignore_dirs) or \
                        any(fnmatch.fnmatch(b_rel_path, b_pattern) for b_pattern in b_ignore_patterns):
                    display.vvv("Skipping '%s' for collection build" % to_text(b_abs_path))
                    continue
                if os.path.islink(b_abs_path):
                    b_link_target = os.path.realpath(b_abs_path)
                    if not b_link_target.startswith(b_top_level_dir):
                        display.warning("Skipping '%s' as it is a symbolic link to a directory outside the collection"
                                        % to_text(b_abs_path))
                        continue
                manifest_entry = entry_template.copy()
                manifest_entry['name'] = rel_path
                manifest_entry['ftype'] = 'dir'
                manifest['files'].append(manifest_entry)
                _walk(b_abs_path, b_top_level_dir)
            else:
                if any(fnmatch.fnmatch(b_rel_path, b_pattern) for b_pattern in b_ignore_patterns):
                    display.vvv("Skipping '%s' for collection build" % to_text(b_abs_path))
                    continue
                manifest_entry = entry_template.copy()
                manifest_entry['name'] = rel_path
                manifest_entry['ftype'] = 'file'
                manifest_entry['chksum_type'] = 'sha256'
                manifest_entry['chksum_sha256'] = secure_hash(b_abs_path, hash_func=sha256)
                manifest['files'].append(manifest_entry)
    _walk(b_collection_path, b_collection_path)
    return manifest
def _build_manifest(namespace, name, version, authors, readme, tags, description, license_ids, license_file,