remember_version() only writes version if called in a Mercurial repository.

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remember_version() only writes version if called in a Mercurial repository.
forget_version() resets version only if remember_version() wrote it.

manifest hash: b30df9d93c233f4bf07150cc5067f294a98c16f4
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mercurial/version.py

@@ -1,62 +1,65
 # Copyright (C) 2005 by Intevation GmbH
 # Author(s):
 # Thomas Arendsen Hein <[e-mail]>
 #
 # This program is free software under the GNU GPL (>=v2)
 # Read the file COPYING coming with the software for details.
 
 """
 Mercurial version
 """
 
 import os
 import os.path
 import re
 import time
 
 unknown_version = 'unknown'
+remembered_version = False
 
 def get_version():
     """Return version information if available."""
     try:
         from mercurial.__version__ import version
     except ImportError:
         version = unknown_version
     return version
 
 def write_version(version):
     """Overwrite version file."""
     filename = os.path.join(os.path.dirname(__file__), '__version__.py')
     f = open(filename, 'w')
     f.write("# This file is auto-generated.\n")
     f.write("version = %r\n" % version)
     f.close()
 
 def remember_version():
     """Store version information."""
+    global remembered_version
+    if os.access(".hg", os.F_OK):
     f = os.popen("hg identify 2>/dev/null")  # use real hg installation
     ident = f.read()[:-1]
     if not f.close() and ident:
         ids = ident.split(' ', 1)
         version = ids.pop(0)
         if version[-1] == '+':
             version = version[:-1]
             modified = True
         else:
             modified = False
         if version.isalnum() and ids:
             for tag in ids[0].split('/'):
                 # is a tag is suitable as a version number?
                 if re.match(r'^(\d+\.)+[\w.-]+$', tag):
                     version = tag
                     break
         if modified:
             version += time.strftime('+%Y%m%d')
-    else:
-        version = unknown_version
+            remembered_version = True
     write_version(version)
 
 def forget_version():
     """Remove version information."""
+    if remembered_version:
     write_version(unknown_version)