##### SUMMARY
The documentation of the module *user* / parameter *shell* states:

https://github.com/ansible/ansible/blob/8edad83ae029d7838a6d6347576d2ddbcce12ad0/lib/ansible/modules/system/user.py#L79

But there are no (shell specific) notes.
##### ISSUE TYPE
- Documentation Report

##### COMPONENT NAME
user / docs

##### ANSIBLE VERSION
devel branch

##### CONFIGURATION
N/A

##### OS / ENVIRONMENT
N/A

##### ADDITIONAL INFORMATION
Either remove the sentence or provide some information in the notes section.

groups = []
            if self.groups == '':
                if current_groups and not self.append:
                    groups_need_mod = True
            else:
                groups = self.get_groups_set(remove_existing=False)
                group_diff = set(current_groups).symmetric_difference(groups)
                if group_diff:
                    if self.append:
                        for g in groups:
                            if g in group_diff:
                                if has_append:
                                    cmd.append('-a')
                                groups_need_mod = True
                                break
                    else:
                        groups_need_mod = True
            if groups_need_mod:
                if self.local:
                    if self.append:
                        lgroupmod_add = set(groups).difference(current_groups)
                        lgroupmod_del = set()
                    else:
                        lgroupmod_add = set(groups).difference(current_groups)
                        lgroupmod_del = set(current_groups).difference(groups)
                else:
                    if self.append and not has_append:
                        cmd.append('-A')
                        cmd.append(','.join(group_diff))
                    else: