fetch-configlet: allow running from the bin directory (#284)

This commit improves the `fetch-configlet` script in two ways:

1. It allows `fetch-configlet` to be run from the `bin` directory itself, instead of requiring it to be run from the repo's root directory.
2. It will output an error if the repo root does not have a `bin` directory.

Co-authored-by: Isaac Good <nuc-git@isaacgood.com>

Author: IsaacG

scripts/fetch-configlet

@@ -45,14 +45,26 @@ get_download_url() {
     cut -d'"' -f4
 }
 
-download_url="$(get_download_url)"
-output_dir="bin"
-output_path="${output_dir}/latest-configlet.${ext}"
-curl "${curlopts[@]}" --output "${output_path}" "${download_url}"
-
-case "${ext}" in
-  *zip) unzip "${output_path}" -d "${output_dir}"   ;;
-  *)    tar xzf "${output_path}" -C "${output_dir}" ;;
-esac
+main () {
+  if [[ -d ./bin ]]; then
+    output_dir="./bin"
+  elif [[ $PWD = */bin ]]; then
+    output_dir="$PWD"
+  else
+    echo "Error: no ./bin directory found. This script should be ran from a repo root." >&2
+    return 1
+  fi
+
+  download_url="$(get_download_url)"
+  output_path="${output_dir}/latest-configlet.${ext}"
+  curl "${curlopts[@]}" --output "${output_path}" "${download_url}"
+
+  case "${ext}" in
+    *zip) unzip "${output_path}" -d "${output_dir}"   ;;
+    *)    tar xzf "${output_path}" -C "${output_dir}" ;;
+  esac
+
+  rm -f "${output_path}"
+}
 
-rm -f "${output_path}"
+main