git commit-msg hook to verify the line lengths of the message

commit-msg

#!/usr/bin/env bash
#
# Usage:
#   Copy to your /usr/share/git-core/templates/hooks directory,
#     and to any existing git repos.
#
# Copy to existing git repos (except those with existing 'commit-msg'):
#   find $HOME -name '.git' -type d -exec test '!' -e "{}/hooks/commit-msg" ';' \
#     -exec cp /usr/share/git-core/templates/hooks/commit-msg "{}/hooks" ';'
#
# Copy to ALL existing git repos (overwrite existing 'commit-msg'):
#   find $HOME -name '.git' -type d \
#     -exec cp /usr/share/git-core/templates/hooks/commit-msg "{}/hooks" ';'
#

# Read commit message,
#   print line number and line
#   put hold each line number, check the length of each line, and print
#     a message if the line is too long.

len_check() {
  local long_lines="$(cat "$1" \
    | sed = \
    | sed -nEe '
  h;n;
  2 { /.{51,}/b toolong
  }
  4 { /.{1,}/b toolong
  }
  6,/# ------/ { /.{73,}/b toolong
  }
  b

  :toolong

  /^#/d
  2i\
  Line too long (limit=50)
  4i\
  Line too long (limit=0)
  6,$ {
  i\
  Line too long (limit=72)
  }

  H
  x
  s/\n/:  /
  s/^/  /
  p')"

  if [[ -n "${long_lines}" ]]
    then
      echo "${long_lines}"
      exit 1
  fi
}

len_check "$@"