When regenerating files like Python-ast.h, take care that the generated

comment based on 'sys.args[0]' does not depend on the path.  For Python
builds from a remote directory ("/path/to/configure; make") the previous
logic used to include the "/path/to" portion in Python-ast.h.  Then svn
would consider this file to be locally modified.

Parser/asdl_c.py

@@ -639,9 +639,8 @@ class ChainOfVisitors:
 
 def main(srcfile):
     argv0 = sys.argv[0]
-    index = argv0.find('/')
-    if index > 0:
-        argv0 = argv0[index + 1:]
+    components = argv0.split(os.sep)
+    argv0 = os.sep.join(components[-2:])
     auto_gen_msg = '/* File automatically generated by %s */\n' % argv0
     mod = asdl.parse(srcfile)
     if not asdl.check(mod):