rewrite revert command. fix issues 93, 123, 147. new version does these things: - saves backup copies of modified files (issue 147) - prints output like other commands, and errors when files not found (issue 123) - marks files added/removed (issue 93)

#!/bin/sh

hg init a
cd a
echo a > foo
hg add foo
hg commit -m 1 -d "1000000 0"
rm foo
hg remove foo
hg commit -m 2 -d "1000000 0"
hg export 0
hg export 1
hg log -p -r 0
hg log -p -r 1

cd ..
hg clone a b