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)
1:016807e6fdaf
0:eb43f19ff115
016807e6fdaf tip
eb43f19ff115
eb43f19ff115+
saving current version of file1 as file1.bak
reverting file1
? file1.bak
eb43f19ff115
? file1.bak
016807e6fdaf tip
merging file1
? file1.bak
016807e6fdaf tip
? file1.bak
016807e6fdaf tip
? file1.bak
016807e6fdaf tip
? file1.bak
016807e6fdaf tip