[__hostname] Add support for Gentoo

cdist/conf/type/__hostname/explorer/persistent_hostname

@@ -41,6 +41,9 @@ in
 	freebsd)
 		(. /etc/rc.conf && echo "$hostname")
 		;;
+	gentoo)
+		(. /etc/conf.d/hostname && echo "$hostname")
+		;;
 	macosx)
 		scutil --get HostName 2>/dev/null
 		;;

cdist/conf/type/__hostname/gencode-remote

@@ -74,14 +74,10 @@ fi
 # Use the good old way to set the hostname. Also if hostnamectl fails.
 case $os
 in
-    archlinux|debian|ubuntu|devuan|coreos|alpine)
+    alpine|archlinux|coreos|debian|devuan|ubuntu)
         echo "printf '%s\\n' '$name_should' > /etc/hostname"
         echo "hostname -F /etc/hostname"
     ;;
-    centos|fedora|redhat|scientific|freebsd|openbsd)
-        # NOTE: Writing the hostname to file is done in the manifest.
-        echo "hostname '$name_should'"
-    ;;
     macosx)
         echo "scutil --set HostName '$name_should'"
     ;;
@@ -91,6 +87,10 @@ in
         echo "printf '%s\\n' '$name_should' > /etc/HOSTNAME"
         echo 'hostname -F /etc/HOSTNAME'
     ;;
+    centos|fedora|freebsd|gentoo|netbsd|openbsd|redhat|scientific)
+        # NOTE: Writing the hostname to file is done in the manifest.
+        echo "hostname '$name_should'"
+    ;;
     *)
         echo "echo 'Unsupported OS: $os' >&2; exit 1"
     ;;

cdist/conf/type/__hostname/manifest

@@ -58,6 +58,13 @@ in
             --key HOSTNAME \
             --value "\"$name_should\""
     ;;
+    gentoo)
+        __key_value confd-hostname \
+            --file /etc/conf.d/hostname \
+            --delimiter '=' --exact_delimiter \
+            --key 'hostname' \
+            --value "\"$name_should\""
+    ;;
     freebsd)
         __key_value rcconf-hostname \
             --file /etc/rc.conf \