hgmerge: do not use file with markers in tools merging themselves
This time I forgot about a crucial part of the logic change.
The patch makes kdiff3 and tkdiff useful again.
transaction abort!
rollback completed
abort: impossible time zone offset: 4444444
transaction abort!
rollback completed
abort: invalid date: '1\t15.1'
transaction abort!
rollback completed
abort: invalid date: 'foo bar'
transaction abort!
rollback completed
abort: invalid date: ' 1 4444'
transaction abort!
rollback completed
abort: date exceeds 32 bits: 111111111111
abort: No such file or directory: .../test/bar