extensions: ignore "sub-options" when looking for extensions

config suboptions are separated by ":" (see the path one for example). So we
dont want to confuse these config with actual extensions.

We don't have extensions sub option yet, but I am about to introduce one for
making sure an extensions can load. So lets level the floor first.

Differential Revision: https://phab.mercurial-scm.org/D11819

mercurial/configitems.py

@@ -1281,7 +1281,7 b' coreconfigitem('
 )
 coreconfigitem(
     b'extensions',
-    b'.*',
+    b'[^:]*',
     default=None,
     generic=True,
 )

mercurial/extensions.py

@@ -282,6 +282,7 b' def loadall(ui, whitelist=None):'
     result = ui.configitems(b"extensions")
     if whitelist is not None:
         result = [(k, v) for (k, v) in result if k in whitelist]
+    result = [(k, v) for (k, v) in result if b':' not in k]
     newindex = len(_order)
     ui.log(
         b'extension',