configitems: register the 'diff.*' config

configitems: register the 'diff.*' config

All the config were already using a unified function with a forced default, so,
registering them all at once seems safe.

--- a/mercurial/configitems.py	Sun Oct 08 20:43:46 2017 +0200
+++ b/mercurial/configitems.py	Sun Oct 08 21:47:14 2017 +0200
@@ -146,6 +146,36 @@
 coreconfigitem('devel', 'strip-obsmarkers',
     default=True,
 )
+coreconfigitem('diff', 'nodates',
+    default=None,
+)
+coreconfigitem('diff', 'showfunc',
+    default=None,
+)
+coreconfigitem('diff', 'unified',
+    default=None,
+)
+coreconfigitem('diff', 'git',
+    default=None,
+)
+coreconfigitem('diff', 'ignorews',
+    default=None,
+)
+coreconfigitem('diff', 'ignorewsamount',
+    default=None,
+)
+coreconfigitem('diff', 'ignoreblanklines',
+    default=None,
+)
+coreconfigitem('diff', 'ignorewseol',
+    default=None,
+)
+coreconfigitem('diff', 'nobinary',
+    default=None,
+)
+coreconfigitem('diff', 'noprefix',
+    default=None,
+)
 coreconfigitem('email', 'charsets',
     default=list,
 )

--- a/mercurial/patch.py	Sun Oct 08 20:43:46 2017 +0200
+++ b/mercurial/patch.py	Sun Oct 08 21:47:14 2017 +0200
@@ -2235,7 +2235,7 @@
                 return v
         if forceplain is not None and ui.plain():
             return forceplain
-        return getter(section, name or key, None, untrusted=untrusted)
+        return getter(section, name or key, untrusted=untrusted)
 
     # core options, expected to be understood by every diff parser
     buildopts = {