tests/test-dirstate-future

patchbomb: fix bug introduced in 4ddfad7ebd98 and add test

Thanks to Augie Fackler for reporting this.

#!/bin/sh

hg init
echo a > a
hg add
hg ci -m1

# set mtime of a into the future
touch -t 202101011200 a

# status must not set a's entry to unset (issue1790)
hg status
hg debugstate