nodes: expand/comment the magic nodes so they are more easily searchable

We just encountered `000000000000modified`, and it was quite annoying to search
for these, even though I knew they existed.  For those that don't know that they
exist, this is essentially impossible to search for :)

(Technically we encountered it in its hex form,
3030303030303030303030306d6f646966696564, so I'm adding comments with those
forms in case that's helpful to people in the future).

Differential Revision: https://phab.mercurial-scm.org/D4331

mercurial/node.py

@@ -1,42 +1,47 b''
 # node.py - basic nodeid manipulation for mercurial
 #
 # Copyright 2005, 2006 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import binascii
 
 # This ugly style has a noticeable effect in manifest parsing
 hex = binascii.hexlify
 # Adapt to Python 3 API changes. If this ends up showing up in
 # profiles, we can use this version only on Python 3, and forward
 # binascii.unhexlify like we used to on Python 2.
 def bin(s):
     try:
         return binascii.unhexlify(s)
     except binascii.Error as e:
         raise TypeError(e)
 
 nullrev = -1
+# In hex, this is '0000000000000000000000000000000000000000'
 nullid = b"\0" * 20
 nullhex = hex(nullid)
 
 # Phony node value to stand-in for new files in some uses of
 # manifests.
-newnodeid = '!' * 20
-addednodeid = ('0' * 15) + 'added'
-modifiednodeid = ('0' * 12) + 'modified'
+# In hex, this is '2121212121212121212121212121212121212121'
+newnodeid = '!!!!!!!!!!!!!!!!!!!!'
+# In hex, this is '0000000000000000000000000000006164646564'
+addednodeid = '000000000000000added'
+# In hex, this is '0000000000000000000000006d6f646966696564'
+modifiednodeid = '000000000000modified'
 
 wdirfilenodeids = {newnodeid, addednodeid, modifiednodeid}
 
 # pseudo identifiers for working directory
 # (they are experimental, so don't add too many dependencies on them)
 wdirrev = 0x7fffffff
+# In hex, this is 'ffffffffffffffffffffffffffffffffffffffff'
 wdirid = b"\xff" * 20
 wdirhex = hex(wdirid)
 
 def short(node):
     return hex(node[:6])