Add script to add practice exercise

TRACK_README.md

@@ -23,15 +23,15 @@ Another benefit is that you don't have to install track-specific dependencies (e
 
 To test a single exercise, run `./bin/verify-exercises-in-docker <exercise-slug>`.
 
-### Track linting
+### Linting
 
 [`configlet`](https://exercism.org/docs/building/configlet) is an Exercism-wide tool for working with tracks. You can download it by running:
 
 ```shell
 $ ./bin/fetch-configlet
 ```
 
-Run its [`lint` command](https://exercism.org/docs/building/configlet/lint) to verify if all exercises have all the necessary files and if config files are correct:
+Run its [`lint` command](https://exercism.org/docs/building/configlet/lint) to verify if exercises have the required files and if config files are correct:
 
 ```shell
 $ ./bin/configlet lint
@@ -53,3 +53,17 @@ Basic linting finished successfully:
 - Required track docs are present
 - Required shared exercise docs are present
 ```
+
+## Adding exercises
+
+New (practice) exercises can be added via:
+
+```shell
+bin/add-practice-exercise <exercise-slug>
+```
+
+Optionally, you can also specify the exercise's difficulty (via `-d`) and/or author's GitHub username (via `-a`):
+
+```shell
+bin/add-practice-exercise -a foobar -d 3 <exercise-slug>
+```

bin/add-practice-exercise

@@ -0,0 +1,84 @@
+#!/usr/bin/env bash
+
+# Synopsis:
+# Scaffold the files for a new practice exercise.
+# After creating the exercise, follow the instructions in the output.
+
+# Example:
+# bin/add-practice-exercise two-fer
+
+# Example with difficulty:
+# bin/add-practice-exercise -d 5 two-fer
+
+# Example with author and difficulty:
+# bin/add-practice-exercise -a foo -d 3 two-fer
+
+set -euo pipefail
+scriptname=$0
+
+help_and_exit() {
+    echo >&2 "Scaffold the files for a new practice exercise."
+    echo >&2 "Usage: ${scriptname} [-h] [-a author] [-d difficulty] <exercise-slug>"
+    echo >&2 "Where: author is the GitHub username of the exercise creator."
+    echo >&2 "Where: difficulty is between 1 (easiest) to 10 (hardest)."
+    exit 1
+}
+
+die() { echo >&2 "$*"; exit 1; }
+
+required_tool() {
+    command -v "${1}" >/dev/null 2>&1 ||
+        die "${1} is required but not installed. Please install it and make sure it's in your PATH."
+}
+
+require_files_template() {
+    jq -e --arg key "${1}" '.files[$key] | length > 0' config.json > /dev/null ||
+        die "The '.files.${1}' array in the 'config.json' file is empty. Please add at least one file. See https://exercism.org/docs/building/tracks/config-json#h-files for more information."
+}
+
+required_tool jq
+
+require_files_template "solution"
+require_files_template "test"
+require_files_template "example"
+
+[[ -f ./bin/fetch-configlet ]] || die "Run this script from the repo's root directory."
+
+author=''
+difficulty='1'
+while getopts :ha:d: opt; do
+    case $opt in
+        h) help_and_exit ;;
+        a) author=$OPTARG ;;
+        d) difficulty=$OPTARG ;;
+        ?) echo >&2 "Unknown option: -$OPTARG"; help_and_exit ;;
+    esac
+done
+shift "$((OPTIND - 1))"
+
+(( $# >= 1 )) || help_and_exit
+
+slug="${1}"
+
+if [[ -z "${author}" ]]; then
+    read -rp 'Your GitHub username: ' author
+fi
+
+./bin/fetch-configlet
+./bin/configlet create --practice-exercise "${slug}" --author "${author}" --difficulty "${difficulty}"
+
+exercise_dir="exercises/practice/${slug}"
+files=$(jq -r --arg dir "${exercise_dir}" '.files | to_entries | map({key: .key, value: (.value | map("'"'"'" + $dir + "/" + . + "'"'"'") | join(" and "))}) | from_entries' "${exercise_dir}/.meta/config.json")
+
+cat << NEXT_STEPS
+
+Your next steps are:
+- Create the test suite in $(jq -r '.test' <<< "${files}")
+  - The tests should be based on the canonical data at 'https://github.com/exercism/problem-specifications/blob/main/exercises/${slug}/canonical-data.json'
+  - Any test cases you don't implement, mark them in 'exercises/practice/${slug}/.meta/tests.toml' with "include = false"
+- Create the example solution in $(jq -r '.example' <<< "${files}")
+- Verify the example solution passes the tests by running 'bin/verify-exercises ${slug}'
+- Create the stub solution in $(jq -r '.solution' <<< "${files}")
+- Update the 'difficulty' value for the exercise's entry in the 'config.json' file in the repo's root
+- Validate CI using 'bin/configlet lint' and 'bin/configlet fmt'
+NEXT_STEPS