hack-install cloud-init from source over the top of a install

hack-install

#!/bin/sh
# this just hacks the current directory (cloud-init source) over the top
# of a install'd deb version
target_d=""
src_d="$PWD"
python="/usr/bin/python3"
error() { echo "$@" 1>&2; }
fail() { [ $# -eq 0 ] || error "$@"; exit 1; }

ref="cloudinit/cloud.py"
if [ -z "$target_d" ]; then
   out=$(dpkg -L cloud-init) || fail "couldnt find installed cloud-init"
   path=$(echo "$out" | grep "$ref$") && [ -f "$path" ] ||
     fail "could not find $ref in installed cloud-init"
   target_d=$(cd "${path%/*}/.." && pwd)
fi

[ -f "$src_d/$ref" ] || fail "$src_d: doesnt have $ref"
echo "target_d=$target_d"
echo "src_d=$src_d"

bins=$(cd "$src_d" && find bin/ -type f) || fail "failed to find bins"
for bin in $bins; do
   [ -f "/usr/bin/${bin#*/}" ] ||
      { error "skipping $bin"; continue; }
   error "binary $bin"
   tfile="/usr/bin/${bin##*/}"
   cp "$bin" "$tfile" || fail "failed cp $bin"
   sed -i '1{/#!.usr.bin.python/s,.*,#!'"$python"',}' "$tfile" ||
      fail "failed fix launcher in $bin"
done

for path in $(cd "$src_d" && find cloudinit -name "*.py" -type f); do
   echo "$path" 1>&2
   cp "$src_d/$path" "$target_d/$path" || fail "failed copy"
done