dirstate: eliminate _lastnormal set We can get rid of the _lastnormal set by using the filesystem mtimes to identify the problematic "lastnormal" files on status(), forcing a file content-comparison if the file's mtime timeslot is equal to _lastnormaltime.

test-extdiff: fix 5c0e1222e7c0 temporary dir output

convert/mtn: avoid unnecessary initial test of mtn repo As soon as before() is called, we'll know if there is a problem (and get a better error message).