revert: distinguish between "check" and "backup" strategy
"check" behaves as backup did before. We check if the current file differs
from destination and we create a backup if it does. This is used for untracked
files that will be overwritten by formerly-deleted files. We have to do the manual
check since no status output can provide the content comparison.
"backup" is now doing unconditional backup. This can be used for files seen as
modified compared to both the target and the working directory. In such a case, we
know that the file differs from target without actually comparing any content.
This new "backup" strategy will be especially useful in the case of files added
between the target and the working directory -parent- with additional modifications
in the working directory -itself-. In that case we know we need to back it up, but we
cannot run the content check as the files does not exists in target.
running: init test1
result: None
running: add foo
result: 0
running: commit -m commit1 -d 2000-01-01 foo
result: None
running: commit -m commit2 -d 2000-01-02 foo
result: None
running: log -r 0
changeset: 0:0e4634943879
user: test
date: Sat Jan 01 00:00:00 2000 +0000
summary: commit1
result: None
running: log -r tip
changeset: 1:45589e459b2e
tag: tip
user: test
date: Sun Jan 02 00:00:00 2000 +0000
summary: commit2
result: None