gen-static-ver

#!/usr/bin/env bash

REPO_DIR="$1"
VERSION="$2"

if [ -z "$REPO_DIR" ] || [ -z "$VERSION" ]; then
	# shellcheck disable=SC2016
	echo 'usage: ./gen-static-ver ${REPO_DIR} ${VERSION}'
	exit 1
fi

GIT_COMMAND="git -C $REPO_DIR"

staticVersion="${VERSION#v}"

# if we have a "-dev" suffix or have change in Git, this is a nightly build, and
# we'll create a pseudo version based on commit-date and -sha.
if [[ "$VERSION" == *-dev ]] || [ -n "$($GIT_COMMAND status --porcelain)" ]; then
	export TZ=UTC

	# based on golang's pseudo-version: https://groups.google.com/forum/#!topic/golang-dev/a5PqQuBljF4
	#
	# using a "pseudo-version" of the form v0.0.0-yyyymmddhhmmss-abcdefabcdef,
	# where the time is the commit time in UTC and the final suffix is the prefix
	# of the commit hash. The time portion ensures that two pseudo-versions can
	# be compared to determine which happened later, the commit hash identifes
	# the underlying commit, and the v0.0.0- prefix identifies the pseudo-version
	# as a pre-release before version v0.0.0, so that the go command prefers any
	# tagged release over any pseudo-version.
	gitUnix="$($GIT_COMMAND log -1 --pretty='%ct')"

	if [ "$(uname)" = "Darwin" ]; then
		# Using BSD date (macOS), which doesn't support the --date option
		# date -jf "<input format>" "<input value>" +"<output format>" (https://unix.stackexchange.com/a/86510)
		gitDate="$(TZ=UTC date -u -jf "%s" "$gitUnix" +'%Y%m%d%H%M%S')"
	else
		# Using GNU date (Linux)
		gitDate="$(TZ=UTC date -u --date "@$gitUnix" +'%Y%m%d%H%M%S')"
	fi

	gitCommit="$($GIT_COMMAND log -1 --pretty='%h')"
	# generated version is now something like '0.0.0-20180719213702-cd5e2db'
	staticVersion="0.0.0-${gitDate}-${gitCommit}" # (using hyphens)
fi

echo "$staticVersion"