posix, windows: introduce cachestat
This class contains a stat result, and possibly other file info to reliably
determine between two points in time whether a file has changed.
Uniquely identifying a file gives us that reliability because we either
atomic rename or append. So one of two will happen: the file 'id' will change,
or the size of the file will change.
posix implements it simply by calling os.stat() and checking if the result
has st_ino.
For now on Windows we always assume the path is uncacheable. This can be
improved on NTFS due to file IDs: http://msdn.microsoft.com/en-us/library/
aa363788(v=vs.85).aspx
So we need to find out if a file path is on an NTFS drive, for that we have:
- GetVolumeInformation, which unfortunately only works with a root path (but is available on XP)
- GetVolumeInformationByHandleW, works on a full file path but requires Vista or higher
$ echo '[Section]' >> $HGRCPATH
$ echo 'KeY = Case Sensitive' >> $HGRCPATH
$ echo 'key = lower case' >> $HGRCPATH
$ hg showconfig Section
Section.KeY=Case Sensitive
Section.key=lower case