Refactor Makefile (#5)

* Improves target handling, script safety, adds self-documenting help

* Remove 'all' target

Makefile

@@ -1,41 +1,52 @@
+# Set the default goal if no targets were specified on the command line
+.DEFAULT_GOAL = run
+# Makes shell non-interactive and exit on any error
+.SHELLFLAGS = -ec
+
 PROJECT_NAME=infomate
 
-all: run
-
-# Install dev requirements
-dev-requirements:
+dev-requirements:  ## Install dev requirements
 	@pip3 install -r requirements.txt
 
-# Migrate database to the latest version
-migrate:
-	@python3 manage.py migrate
-
-# Check types with mypy
-mypy:
-	mypy $(PROJECT_NAME)
-
-# Lint code with flake8
-lint:
-	flake8 $(PROJECT_NAME)
-
-# Runs dev server
-run:
-	@python3 manage.py runserver
-
-# Run dev server in docker
-docker_run:
+docker_run:  ## Run dev server in docker
 	@python3 ./utils/wait_for_postgres.py
 	@python3 manage.py migrate
 	@python3 manage.py runserver
 
-# Initialize feeds from boards.yml
-feed_init:
+feed_cleanup:  ## Cleanup RSS feeds
+	@python3 ./scripts/cleanup.py
+
+feed_init:  ## Initialize feeds from boards.yml
 	@python3 ./scripts/initialize.py
 
-# Refresh RSS feeds
-feed_refresh:
+feed_refresh:  ## Refresh RSS feeds
 	@python3 ./scripts/update.py
 
-# Cleanup RSS feeds
-feed_cleanup:
-	@python3 ./scripts/cleanup.py
+help:  ## Display this help
+	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) \
+	  | sort \
+	  | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[0;32m%-30s\033[0m %s\n", $$1, $$2}'
+
+lint:  ## Lint code with flake8
+	flake8 $(PROJECT_NAME)
+
+migrate:  ## Migrate database to the latest version
+	@python3 manage.py migrate
+
+mypy:  ## Check types with mypy
+	mypy $(PROJECT_NAME)
+
+run:  ## Runs dev server
+	@python3 manage.py runserver
+
+.PHONY: \
+  dev-requirements \
+  docker_run \
+  feed_cleanup \
+  feed_init \
+  feed_refresh \
+  help \
+  lint \
+  migrate \
+  mypy \
+  run