pre-commit.sample: add comment re tr portability; fix grammar
pre-commit.sample: add comment re tr portability; fix grammar

Add a comment explaining why square brackets around a tr range
are not only ok, but actually required in this case.
Correct spelling and grammar.

Signed-off-by: Jim Meyering <15b0b14300fba1cff8c70eb2a5c1720ef2a4c654@redhat.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git