ui: don't fixup [paths] sub-options

As part of developing a subsequent patch I discovered that sub-option
values like "." were getting converted to paths. This is because the
[paths] section is treated specially during config loading.

This patch prevents post-processing sub-options from the [paths]
section.

mercurial/ui.py

@@ -228,6 +228,9 b' class ui(object):'
             root = root or os.getcwd()
             for c in self._tcfg, self._ucfg, self._ocfg:
                 for n, p in c.items('paths'):
+                    # Ignore sub-options.
+                    if ':' in n:
+                        continue
                     if not p:
                         continue
                     if '%%' in p:

tests/test-config.t

@@ -90,3 +90,15 b' Test exit code when no config matches'
 
   $ hg config Section.idontexist
   [1]
+
+sub-options in [paths] aren't expanded
+
+  $ cat > .hg/hgrc << EOF
+  > [paths]
+  > foo = ~/foo
+  > foo:suboption = ~/foo
+  > EOF
+
+  $ hg showconfig paths
+  paths.foo:suboption=~/foo
+  paths.foo=$TESTTMP/foo