Run check-typo over merge commit
Run check-typo over merge commit

When checking an entire branch, check-typo was reading files from the
tip of the pull request branch, which is only correct if the branch is
based on trunk - it should read from the merge commit instead.

This affects branches based on older trunk before check-typo compliance
was enforced, since it can cause now-corrected check-typo violations to
re-appear.

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml