Exclude "merged" files from merge commit

[Marc Strapetz]

For some kind of conflicts, where the file in the merge target has
diverged too much from the merge source, resolution is to not apply any
changes from the source at all. Here one will usually do a "hg resolve
--mark file" and "hg discard -r <working-revision> file". Still the file
will show up as modified when invoking "hg status" and it will be
included for the commit (as "hg debugdata -c" tells me).

Sometimes this may be appropriate to denote that the file has been
merged (but without any changes), sometimes it may be more appropriate
to not have the file included for the merge commit at all. Is there a
way to achieve this? E.g. by resetting "merged" flag in .hg/dirstate?

-Marc