doc: Document the tag `master_fill_policy`

lib/awful/tag.lua

@@ -889,7 +889,13 @@ function tag.getgap(t, numclients)
     return tag.object.get_gap(t or ascreen.focused().selected_tag)
 end
 
---- The default fill policy
+--- The default fill policy.
+--
+-- ** Possible values**:
+--
+-- * *expand*: Take all the space
+-- * *master_width_factor*: Only take the ratio defined by the
+--   `master_width_factor`
 --
 -- @beautiful beautiful.master_fill_policy
 -- @param string (default: "expand")
@@ -897,6 +903,12 @@ end
 
 --- Set size fill policy for the master client(s).
 --
+-- ** Possible values**:
+--
+-- * *expand*: Take all the space
+-- * *master_width_factor*: Only take the ratio defined by the
+--   `master_width_factor`
+--
 -- **Signal:**
 --
 -- * *property::master_fill_policy*

tests/test-awful-layout.lua

@@ -76,8 +76,8 @@ local common_steps = {
         return true
     end,
     function()
-        t.master_fill_policy = t.master_fill_policy == "mwfact" and
-            "expand" or "mwfact"
+        t.master_fill_policy = t.master_fill_policy == "master_width_factor" and
+            "expand" or "master_width_factor"
 
         return true
     end,