merge: backout manifest sorting and workarounds for cost of it
Backout
8a811fa9a9c0 and
760c0d67ce5e which no longer are needed.
merge: delay debug messages for merge actions
Show messages at a point where the actions have been sorted, thus preparing for
backout of
760c0d67ce5e.
This makes manifestmerge more of a silent operation, just like 'copies' is.
Indent 'preserving' messages to make them subordinate to the action logging so
they fit in the new context. (The 'preserving' messages are quite redundant and
could also be removed completely.)