Script to print Go module v0.0.0-DATE-SHA version strings

gomodver

#!/bin/bash
# Usage: gomodver [REF...]
# Prints a Go modules v0.0.0-DATE-SHA version string for the given Git refs.
# If no REF is given, gomodver defaults to HEAD.

datearg=d@
case "$(uname -s | tr A-Z a-z)" in
*bsd|darwin) datearg=r;
esac

if [ $# -eq 0 ]; then
  set -- HEAD
fi
nl=''
for ref; do
  head="$(git rev-parse "$ref")"
  shortsha="${head:0:12}"
  ts="$(git log -n1 --date=raw --format='%cd' "$head" | cut -f1 -d' ')"
  committed="$(date "-${datearg}${ts}" -u '+%Y%m%d%H%M%S')"
  printf "%sv0.0.0-%s-%s" "${nl}" "${committed}" "${shortsha}"
  nl=$'\n'
done
if [ -t 1 ]; then
  printf '\n'
fi