interhg: use uisetup() instead of module-load side effects

This fixes an infinite recursion bug caused by visiting a bad subpage
of the help handler repeatedly, which caused the wrapper for the
templater's escape filter to get installed twice and resulted in
infinite recursion.

hgext/interhg.py

@@ -28,17 +28,18 b' from mercurial.hgweb import hgweb_mod'
 from mercurial import templatefilters, extensions
 from mercurial.i18n import _
 
-orig_escape = templatefilters.filters["escape"]
-
 interhg_table = []
 
-def interhg_escape(x):
-    escstr = orig_escape(x)
-    for regexp, format in interhg_table:
-        escstr = regexp.sub(format, escstr)
-    return escstr
+def uisetup(ui):
+    orig_escape = templatefilters.filters["escape"]
 
-templatefilters.filters["escape"] = interhg_escape
+    def interhg_escape(x):
+        escstr = orig_escape(x)
+        for regexp, format in interhg_table:
+            escstr = regexp.sub(format, escstr)
+        return escstr
+
+    templatefilters.filters["escape"] = interhg_escape
 
 def interhg_refresh(orig, self, *args, **kwargs):
     interhg_table[:] = []