merge: allow merging going backwards
New behavior is generally superior and more correct, except possibly
with regards to missing files. hg up . is now effectively a no-op,
which is probably the desired behavior for people expecting to move to
tip, but may surprise people who were expecting deleted files to
reappear.
case 1: update to .
a-w -> a-w
classic: ancestor a
missing recreated right?
rmed recreated WRONG
added forgotten WRONG
changed preserved RIGHT
conflicted can't happen
backward merge: ancestor a (NO EFFECT)
missing missing wrong?
rm'ed rm'ed RIGHT
added preserved RIGHT
changed preserved RIGHT
conflicted can't happen
case 2: update to ancestor of .
a-b-w -> b-w
\
a
classic: ancestor a
missing recreated right?
rmed recreated wrong?
added forgotten wrong?
changed preserved RIGHT
conflicted preserved wrong?
backwards merge: ancestor b
missing missing or conflict right?
rm'ed missing or conflict right?
changed preserved RIGHT
conflicted merge RIGHT
added preserved right?
adding a
79abf14474dc tip
% make sure we notice the change of mode if the cached size == -1
n 0 -1 unset a
M a
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
d69afc33ff8a
not executable -- whew