CONTRIBUTING: link to PR guide.
mercury 14.01
mercury: update 14.01 bottle.

Closes #30530.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
CONTRIBUTING: fix dashes.
Use accessor method in test
verliator 3.862
nudge formatting

Needed for Emacs' ruby highlighting to work past this point in the file.
Fix checking out recursive git submodules

When nested submodules appear in a git repository, the `git submodule foreach
git checkout-index ..` command would fail because it would checkout at the root
directory instead of in its parent(s)' folder.

Eg: root/submodule1/submodule2 would be checked out in root/submodule2