The hook was added in a86ed83cce (Merge branch 'tr/notes-display' -
2010-03-24), which updated githooks.txt but not git-commit.txt.
git-commit.txt was later updated in e858af6d50 (commit: document a
couple of options - 2012-06-08). Since this commit focused on command
line options, this section was probably forgotten.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>