gentoo: fix hostname rendering when value has a comment (#611)

Gentoo's hostname file format instead of being just the host name
is hostname=thename". The old code works fine when the file has no comments
but if there is a comment the line

```
gentoo_hostname_config = 'hostname="%s"' % conf
```

can render an invalid hostname file that looks similar to

```
hostname="#This is the host namehello"
```

The fix inserts the hostname in a gentoo friendly way so that it gets
handled by HostnameConf as a whole and comments are handled and preserved

cloudinit/distros/gentoo.py

@@ -160,10 +160,12 @@ def _write_hostname(self, your_hostname, out_fn):
             pass
         if not conf:
             conf = HostnameConf('')
-        conf.set_hostname(your_hostname)
-        gentoo_hostname_config = 'hostname="%s"' % conf
-        gentoo_hostname_config = gentoo_hostname_config.replace('\n', '')
-        util.write_file(out_fn, gentoo_hostname_config, 0o644)
+
+        # Many distro's format is the hostname by itself, and that is the
+        # way HostnameConf works but gentoo expects it to be in
+        #     hostname="the-actual-hostname"
+        conf.set_hostname('hostname="%s"' % your_hostname)
+        util.write_file(out_fn, str(conf), 0o644)
 
     def _read_system_hostname(self):
         sys_hostname = self._read_hostname(self.hostname_conf_fn)

tests/unittests/test_distros/test_gentoo.py

@@ -0,0 +1,26 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+
+from cloudinit import util
+from cloudinit import atomic_helper
+from cloudinit.tests.helpers import CiTestCase
+from . import _get_distro
+
+
+class TestGentoo(CiTestCase):
+
+    def test_write_hostname(self):
+        distro = _get_distro("gentoo")
+        hostname = "myhostname"
+        hostfile = self.tmp_path("hostfile")
+        distro._write_hostname(hostname, hostfile)
+        self.assertEqual('hostname="myhostname"\n', util.load_file(hostfile))
+
+    def test_write_existing_hostname_with_comments(self):
+        distro = _get_distro("gentoo")
+        hostname = "myhostname"
+        contents = '#This is the hostname\nhostname="localhost"'
+        hostfile = self.tmp_path("hostfile")
+        atomic_helper.write_file(hostfile, contents, omode="w")
+        distro._write_hostname(hostname, hostfile)
+        self.assertEqual('#This is the hostname\nhostname="myhostname"\n',
+                         util.load_file(hostfile))

tools/.github-cla-signers

@@ -13,6 +13,7 @@ johnsonshi
 jqueuniet
 landon912
 lucasmoura
+manuelisimo
 marlluslustosa
 matthewruffell
 nishigori