Spent all day on some horrible timestamp issues on legacy systems. 

On FAT, timestamps have a 2s granularity, which is ok, but then Linux adds
a temporary higher resolution cache, which is lost on unmount. This
confused git-annex since the mtimes seemed to change and it had to
re-checksum half the files to get unconfused, which was not good.
I found a way to use the inode sentinal file to detect when on FAT
and put in a workaround, without degrading git-annex everywhere else.

On Windows, time zones are a utter disaster; it changes the mtime it reports
for files after the time zone has changed. Also there's a bug in the
haskell time library which makes it return old time zone data after a time
zone change. (I just finished developing a fix for that bug..)

Left with nothing but a few sticks, I rubbed them together, and
actually found a way to deal with this problem too. Scary details in
[[bugs/Windows_file_timestamp_timezone_madness]]. While I've implemented
it, it's stuck on a branch until I find a way to make git-annex notice when
the timezone changes while it's running.

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Today's work was sponsored by Svenne Krap.