Add state option to git_config module (#50578)

* Add state option to git_config module

State present/absent option works like --set/--unset option for 'git config'.

* Change git_config to avoid useless parameter passed to git command

When unsetting value, command was : git config --unset foo ''.
Now command is : git config --unset foo.

* Add some integration tests to git_config module

* Add missing aliases file

* Change set up method

Using git command seems to cause troubles on some OS : changing config
by changing '.gitconfig' file.

* Remove some distros from tests pool

Git is not installed or is out of date on these distros.

* Fix aliases to skip tests on centos6

* Refactor tests of the git_config module

* Add use case when state=absent and value is defined

lib/ansible/modules/source_control/git_config.py

@@ -51,6 +51,14 @@ options:
         also specify the repo parameter. It defaults to system only when
         not using I(list_all)=yes.
     choices: [ "local", "global", "system" ]
+  state:
+    description:
+      - "Indicates the setting should be set/unset.
+        This parameter has higher precedence than I(value) parameter:
+        when I(state)=absent and I(value) is defined, I(value) is discarded."
+    choices: [ 'present', 'absent' ]
+    default: 'present'
+    version_added: '2.8'
   value:
     description:
       - When specifying the name of a single setting, supply a value to
@@ -69,6 +77,12 @@ EXAMPLES = '''
     scope: global
     value: status
 
+# Unset some settings in ~/.gitconfig
+- git_config:
+    name: alias.ci
+    scope: global
+    state: absent
+
 # Or system-wide:
 - git_config:
     name: alias.remotev
@@ -149,9 +163,10 @@ def main():
             name=dict(type='str'),
             repo=dict(type='path'),
             scope=dict(required=False, type='str', choices=['local', 'global', 'system']),
+            state=dict(required=False, type='str', default='present', choices=['present', 'absent']),
             value=dict(required=False)
         ),
-        mutually_exclusive=[['list_all', 'name'], ['list_all', 'value']],
+        mutually_exclusive=[['list_all', 'name'], ['list_all', 'value'], ['list_all', 'state']],
         required_if=[('scope', 'local', ['repo'])],
         required_one_of=[['list_all', 'name']],
         supports_check_mode=True,
@@ -175,6 +190,12 @@ def main():
     else:
         scope = 'system'
 
+    if params['state'] == 'absent':
+        unset = 'unset'
+        params['value'] = None
+    else:
+        unset = None
+
     if params['value']:
         new_value = params['value']
     else:
@@ -212,16 +233,22 @@ def main():
             k, v = value.split('=', 1)
             config_values[k] = v
         module.exit_json(changed=False, msg='', config_values=config_values)
-    elif not new_value:
+    elif not new_value and not unset:
         module.exit_json(changed=False, msg='', config_value=out.rstrip())
+    elif unset and not out:
+        module.exit_json(changed=False, msg='no setting to unset')
     else:
         old_value = out.rstrip()
         if old_value == new_value:
             module.exit_json(changed=False, msg="")
 
     if not module.check_mode:
-        new_value_quoted = shlex_quote(new_value)
-        cmd = ' '.join(args + [new_value_quoted])
+        if unset:
+            args.insert(len(args) - 1, "--" + unset)
+            cmd = ' '.join(args)
+        else:
+            new_value_quoted = shlex_quote(new_value)
+            cmd = ' '.join(args + [new_value_quoted])
         (rc, out, err) = module.run_command(cmd, cwd=dir)
         if err:
             module.fail_json(rc=rc, msg=err, cmd=cmd)
@@ -232,7 +259,7 @@ def main():
             before_header=' '.join(args),
             before=old_value + "\n",
             after_header=' '.join(args),
-            after=new_value + "\n"
+            after=(new_value or '') + "\n"
         ),
         changed=True
     )