generate_man_page_date.sh

#! /bin/sh

# generate_man_page_date.sh - find a suitable date for the man page
# Copyright (C) 2021-2023  Erik Auerswald <auerswal@unix-ag.uni-kl.de>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

# when in a git repository, use modification date of man page source
if type 'git' >/dev/null 2>&1 && test -d '.git'; then
  git log -n1 --date=short 'section.1.in' | awk '/^Date:/ { print $2 }'
  exit
fi
# when a man page is available, keep its date
# the generated man page is included in the tar ball for this to work
# this allows to use the most accurate information when working from a tar ball,
# as long as the included man page is not deleted, e.g., via "make distclean"
if test -f 'section.1' && test -r 'section.1'; then
  awk 'NR == 1 { gsub(/"/, "", $4); print $4; exit }' 'section.1'
  exit
fi
# for a released version, use the release date
# this allows for reproducible man page builds when working from a tar ball
# of a release version after "make distclean"
VERSION=$(sed -En 's/^.*VERSION.*=.*"([0-9]+(\.[0-9]+){2}\+?)".*$$/\1/p' section.go)
if test -n "$VERSION" && echo "$VERSION" | grep -qv '+$'; then
  RELDATE=$(sed -En "s/^Version $VERSION \\(([0-9]{4}-[0-9]{2}-[0-9]{2})\).*$/\1/p" NEWS)
  if test -n "$RELDATE"; then
    echo "$RELDATE"
    exit
  fi
fi
# as a last resort, use the file modification date of man page source
date -r 'section.1.in' +%Y-%m-%d