ENH: improve speed/flexibility of pre-commit-hook

- only search indexed files (BUGFIX)
- search for long-lines is faster when regex is anchored
- use git grep logic instead of sed logic where possible

- add support for running the hook manually as well.
  For example,
      bin/tools/pre-commit-hook  applications/test src/OpenFOAM/db

- add some feedback to pre-commit hook:
  The hook can be really slow, at least let people know that something
  is happening