This is by design. Rebase does not rebase merge commits because it is
assumed that merge commits only do what their name implies - to merge
branches of a forked history. As such, they do not introduce their own
changes. Follow this rule, i.e., make your change in a separate non-merge
commit, and you are fine.
Doesn't this create a problem if you pull, resolve a conflit but do NOT
push, then pull --rebase some more commits later on? As I understand
it, the conflict resolution commit will be a merge commit and will be
thrown away by the git pull --rebase.
Philippe