git-info.sh

#!/bin/bash
# ----------------------------------------
# Print git metadata for the current repo
# ----------------------------------------
# metadata: 
#  date: ISO8601 timestamp
#  sha: SHA short (7-digit)
#  sha_full: SHA 40-digit
#
# optionally create a bash variable prefix, which is useful for eval statements
#
#   $ git-info sha appname
#   appname_sha=34abc67
#
#  thus: 
#   
#   $ eval $(git-info.sh sha appname)
#   $ echo $appname_sha
#   34abc67
#
set -e

what=${1:-all}         # print: all | date | sha | sha_full
if [[ $1 ]] ; then
shift 1
fi
prefix="${@}"   # prefix this string to all output

# ------------------------------------
# Convert UNIX timestamp (seconds since epoch UTC) to YYYY-MM-DDTHH:MM:SSZ
# ------------------------------------
function unix_to_iso() {
  declare ts=${1}
 
  declare formatOutput="+%FT%TZ"
  case $(uname -s) in
    ( Darwin )
       TZ=UTC date -j -r $ts $formatOutput
      ;;
    ( Linux )
      TZ=UTC date -d @$ts $formatOutput
      ;;
  esac
}
 
# ------------------------------------
# Get the git metadata for the current project
# ------------------------------------
declare -a versionMetadata=( $(TZ=UTC git log -n 1 --pretty="%ct %h %H") )
declare versionDate=$(unix_to_iso ${versionMetadata[0]})
declare versionSHA=${versionMetadata[1]}
declare versionSHAFull=${versionMetadata[2]}

case $what in
  ( all | date ) printf "${prefix:+${prefix}_date=}${versionDate}\n" ;;&
  ( all | sha ) printf "${prefix:+${prefix}_sha=}${versionSHA}\n" ;;&
  ( all | sha_full ) printf "${prefix:+${prefix}_sha_full=}${versionSHAFull}\n" ;;&
esac