[RFC] Add config option corresponding to --rebase-merges

[Dakota Hawkins <dakota@dakotahawkins.com>]

I'd like to work on a patch to add config options that correspond to
rebase's --rebase-merges flag.

In my workflow, while it's uncommon to encounter merge commits during
a rebase operation, when they are encountered I pretty much always
want this behavior. Since it's rare, I pretty much always forget to
ask for it, with interesting and confusing consequences.

If nobody has any opposition to the concept, the following are the
specific options and values that I think makes sense and covers the
existing functionality.

# New rebase.merges config that takes effect if set to true or cousins
+ rebase.merges=
+   true
+   cousins

# New cousins value for pull.rebase
pull.rebase=
+   cousins

# New pull.rebaseMerges config that takes effect if set to true or
# cousins. Intended to allow pull.rebase to be set to interactive.
+ pull.rebaseMerges=
+   true
+   cousins

# Corresponding additions for branch.<name> config
branch.<name>.rebase=
+   cousins
branch.<name>.rebaseMerges=
+   true
+   cousins

I'd like to get feedback on the idea and specific options proposed,
if only to avoid having to tweak them once they've been added.

Thanks,

Dakota Hawkins