Add pre-commit hooks of our own

Adds some basic near-universal checks and shellcheck

.pre-commit-config.yaml

@@ -0,0 +1,14 @@
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.2.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-yaml
+        args:
+          - --allow-multiple-documents
+      - id: check-merge-conflict
+  - repo: https://github.com/shellcheck-py/shellcheck-py
+    rev: v0.7.1.1
+    hooks:
+      - id: shellcheck

Makefile

@@ -1,13 +1,9 @@
 .PHONY: all test clean
 
-all: test shellcheck
+all: check test
 
 test: test-negative test-positive
 
-.PHONY: shellcheck
-shellcheck:
-	shellcheck *.sh
-
 .PHONY: test-positive
 test-positive:
 	@echo "Check valid compose file."
@@ -19,3 +15,13 @@ test-negative:
 	./compose-check.sh tests/docker-compose.bad.yml && { echo 'fail'; exit 1; } || echo 'ok'
 	@echo "Check multiple files. Should error."
 	./compose-check.sh tests/docker-compose* && { echo 'fail'; exit 1; } || echo 'ok'
+
+# Installs pre-commit hooks
+.PHONY: install-hooks
+install-hooks:
+	pre-commit install --install-hooks
+
+# Checks files for encryption
+.PHONY: check
+check:
+	pre-commit run --all-files