backout: deprecate/hide support for backing out merges
This has never worked usefully:
- it can't undo a completely unwanted merge, as it leaves the merge in the DAG
- it can't undo a faulty merge as that means doing a merge correctly,
not simply reverting to one or the other parent
Both of these kinds of merge also require coordinated action among
developers to avoid the bad merge continuing to affect future merges,
so we should stop pretending that backout is of any help here.
As backing out a merge now requires a hidden option, it can't be done
by accident, but will continue to 'work' for anyone who's already
dependent on --parent for some unknown reason.
$ cat <<EOF >> $HGRCPATH
> [extensions]
> purge =
> EOF
$ hg init test
$ cd test
$ echo a > changed
$ echo a > removed
$ echo a > source
$ hg ci -Am addfiles
adding changed
adding removed
adding source
$ echo a >> changed
$ echo a > added
$ hg add added
$ hg rm removed
$ hg cp source copied
$ hg diff --git > ../unknown.diff
Test adding on top of an unknown file
$ hg up -qC 0
$ hg purge
$ echo a > added
$ hg import --no-commit ../unknown.diff
applying ../unknown.diff
file added already exists
1 out of 1 hunks FAILED -- saving rejects to file added.rej
abort: patch failed to apply
[255]
Test modifying an unknown file
$ hg revert -aq
$ hg purge
$ hg rm changed
$ hg ci -m removechanged
$ echo a > changed
$ hg import --no-commit ../unknown.diff
applying ../unknown.diff
abort: cannot patch changed: file is not tracked
[255]
Test removing an unknown file
$ hg up -qC 0
$ hg purge
$ hg rm removed
$ hg ci -m removeremoved
created new head
$ echo a > removed
$ hg import --no-commit ../unknown.diff
applying ../unknown.diff
abort: cannot patch removed: file is not tracked
[255]
Test copying onto an unknown file
$ hg up -qC 0
$ hg purge
$ echo a > copied
$ hg import --no-commit ../unknown.diff
applying ../unknown.diff
abort: cannot create copied: destination already exists
[255]