ftruncate() and open() with O_TRUNC shall upon successful completion
mark for update the st_ctime and st_mtime fields of the file.
truncate() shall upon successful completion, if the file size is
changed, mark for update the st_ctime and st_mtime fields of the file.
The POSIX standard "The Open Group Base Specifications Issue 7", IEEE
Std 1003.1, 2013 Edition says nothing about the behaviour of truncate()
if the file size remains unchanged.
Future directions of the standard may mandate the behaviour specified in
ftruncate():
http://austingroupbugs.net/view.php?id=489
Script does what is expected and tries to do it as
smartly as possible.
+ remove occurrences of two blank comment lines
next to each other after Id string line removed.
+ remove entire comment blocks which only exited to
contain CVS Ids
+ If the processing left a blank line at the top of
a file, it was removed.
