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.
Previously, when rolling back a transaction, some users could be confused
between the level to which the store is rolled back, and the new parents
of the working directory.
$ hg rollback
rolling back to revision 4 (undo commit)
With this change:
$ hg rollback
repository tip rolled back to tip revision 4 (undo commit)
working directory now based on revision 2 and 1
So now the user can realize that the store has been rolled back to an older
tip, but also that the working directory may not on the tip (here we are
rolling back the merge of the heads 2 and 1)
This changes backouts changeset to retain linear history, .e. it is committed
as a child of the working directory parent, not the reverted changeset
parent.
The default behavior was previously to just commit a reverted change as a
child of the backed out changeset - thus creating a new head. Most of
the time, you would use the --merge option, as it does not make sense to
keep this dangling head as is.
The previous behavior could be obtained by using 'hg update --clean .' after a
'hg backout --merge'.
The --merge option itself is not affected by this change. There is also
still an autocommit of the backout if a merge is not needed, i.e. in case
the backout is the parent of the working directory.
Previously we had (pwd = parent of the working directory):
pwd older
backout auto merge
backout --merge auto commit
With the new linear approach:
pwd older
backout auto commit
backout --merge auto commit
auto: commit done by the backout command
merge: backout also already committed but explicit merge and commit needed
commit: user need to commit the update/merge
