"git pull --rebase --recurse-submodules" checked for local changes
in a wrong range and failed to run correctly when it should.
* pb/pull-rebase-recurse-submodules:
pull: check for local submodule modifications with the right range
t5572: describe '--rebase' tests a little more
t5572: add notes on a peculiar test
pull --rebase: compute rebase arguments in separate function