[PATCH 1 of 5] pycompat: introduce identity function as a compat stub

[Yuya Nishihara]

# HG changeset patch
# User Yuya Nishihara <yuya at tcha.org>
# Date 1490789635 -32400
#      Wed Mar 29 21:13:55 2017 +0900
# Node ID 267ba0ee66701fa87ff1764323599c299cff3e1f
# Parent  d73490957d6162edf064055e40b321ee819187d2
pycompat: introduce identity function as a compat stub

I was sometimes too lazy to use 'str' instead of 'lambda a: a'. Let's add
a named function for that purpose.

diff --git a/mercurial/encoding.py b/mercurial/encoding.py
--- a/mercurial/encoding.py
+++ b/mercurial/encoding.py
@@ -211,8 +211,8 @@ if pycompat.ispy3:
     strtolocal = unitolocal
     strfromlocal = unifromlocal
 else:
-    strtolocal = str
-    strfromlocal = str
+    strtolocal = pycompat.identity
+    strfromlocal = pycompat.identity
 
 if not _nativeenviron:
     # now encoding and helper functions are available, recreate the environ
diff --git a/mercurial/pycompat.py b/mercurial/pycompat.py
--- a/mercurial/pycompat.py
+++ b/mercurial/pycompat.py
@@ -30,6 +30,9 @@ else:
     import socketserver
     import xmlrpc.client as xmlrpclib
 
+def identity(a):
+    return a
+
 if ispy3:
     import builtins
     import functools
@@ -206,9 +209,7 @@ else:
     bytechr = chr
     bytestr = str
     iterbytestr = iter
-
-    def sysstr(s):
-        return s
+    sysstr = identity
 
     # Partial backport from os.py in Python 3, which only accepts bytes.
     # In Python 2, our paths should only ever be bytes, a unicode path
@@ -222,17 +223,13 @@ else:
 
     # In Python 2, fsdecode() has a very chance to receive bytes. So it's
     # better not to touch Python 2 part as it's already working fine.
-    def fsdecode(filename):
-        return filename
+    fsdecode = identity
 
     def getoptb(args, shortlist, namelist):
         return getopt.getopt(args, shortlist, namelist)
 
-    def strkwargs(dic):
-        return dic
-
-    def byteskwargs(dic):
-        return dic
+    strkwargs = identity
+    byteskwargs = identity
 
     osname = os.name
     ospathsep = os.pathsep