Bash script to fetch, edit, and write back a Concourse pipeline

fly-edit-pipeline

#!/bin/bash
set -euo pipefail

TARGET=${1:-}
PIPELINE=${2:-}

FLY=$(which fly)
TEMPDIR=$(mktemp -d -t concourse)

cleanup() {
  rm -rf "$TEMPDIR"
}
trap cleanup EXIT

fail() {
  echo "$*" >&2
  exit 1
}

usage() {
  echo "Usage: $0 TARGET PIPELINE" >&2
  exit 2
}

checksum() {
  local file="$1"
  cat "$file" | md5
}

write_header() {
  local file="$1"
  printf "# Pipeline $PIPELINE in target $TARGET\n---\n" >"$file"
}

get_pipeline() {
  local file="$1"
  write_header "$file"
  "$FLY" -t $TARGET get-pipeline -p $PIPELINE >>"$file"
}

set_pipeline() {
  local file="$1"
  "$FLY" -t $TARGET set-pipeline -p $PIPELINE -c "$file"
}

edit_pipeline() {
  local file="$TEMPDIR/pipeline.yml"
  local old_checksum

  get_pipeline "$file"
  old_checksum=$(checksum "$file")

  nvim -n -- "$file"

  if [ $old_checksum = $(checksum "$file") ]
  then echo "No changes to pipeline"
  else set_pipeline "$file"
  fi
}

[ -n "$TARGET" ] || usage
[ -n "$PIPELINE" ] || usage
[ -x "$FLY" ] || fail "fly command not executable: $FLY"

edit_pipeline