changelog: turn {de,en}code_extra methods into functions

The methods were not really methods -- they didn't use 'self'. Having
them as functions in the module it useful for other modules (like the
commitsigs extension) that want to recompute the changeset hash and
thus want to encode dicts the same way as changelog does it.

Removed the underbars from their names at the same time.

mercurial/changelog.py

@@ -23,6 +23,19 b' def _string_escape(text):'
     text = text.replace('\\', '\\\\').replace('\n', '\\n').replace('\r', '\\r')
     return text.replace('\0', '\\0')
 
+def decodeextra(text):
+    extra = {}
+    for l in text.split('\0'):
+        if l:
+            k, v = l.decode('string_escape').split(':', 1)
+            extra[k] = v
+    return extra
+
+def encodeextra(d):
+    # keys must be sorted to produce a deterministic changelog entry
+    items = [_string_escape('%s:%s' % (k, d[k])) for k in sorted(d)]
+    return "\0".join(items)
+
 class appender:
     '''the changelog index must be updated last on disk, so we use this class
     to delay writes to it'''
@@ -145,19 +158,6 b' class changelog(revlog.revlog):'
             return
         return revlog.revlog.checkinlinesize(self, tr, fp)
 
-    def decode_extra(self, text):
-        extra = {}
-        for l in text.split('\0'):
-            if l:
-                k, v = l.decode('string_escape').split(':', 1)
-                extra[k] = v
-        return extra
-
-    def encode_extra(self, d):
-        # keys must be sorted to produce a deterministic changelog entry
-        items = [_string_escape('%s:%s' % (k, d[k])) for k in sorted(d)]
-        return "\0".join(items)
-
     def read(self, node):
         """
         format used:
@@ -192,7 +192,7 b' class changelog(revlog.revlog):'
         else:
             time, timezone, extra = extra_data
             time, timezone = float(time), int(timezone)
-            extra = self.decode_extra(extra)
+            extra = decodeextra(extra)
         if not extra.get('branch'):
             extra['branch'] = 'default'
         files = l[3:]
@@ -218,7 +218,7 b' class changelog(revlog.revlog):'
         if extra and extra.get("branch") in ("default", ""):
             del extra["branch"]
         if extra:
-            extra = self.encode_extra(extra)
+            extra = encodeextra(extra)
             parseddate = "%s %s" % (parseddate, extra)
         l = [hex(manifest), user, parseddate] + sorted(files) + ["", desc]
         text = "\n".join(l)