[mutter] Non-fast-forward update to branch wip/lantw/monitor-transform-Don't-call-abs-on-non-negative-enum

[Ting-Wei Lan <lantw src gnome org>]

The branch 'wip/lantw/monitor-transform-Don't-call-abs-on-non-negative-enum' was changed in a way that was 
not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  cedbb85... monitor-transform: Don't call abs on non-negative enum

Commits added to the branch:

  4dafcb5... monitor-transform: Don't call abs on non-negative enum