Add verify-commit script for pre-commit style check

scripts/verify-commit

@@ -0,0 +1,46 @@
+#!/bin/bash
+
+# verify-commit:
+#  Ensures that a diff doesn't introduce code that clang-format would change
+
+# Can be executed as a pre-commit hook by symlinking this script:
+#  $ ln -s .git/hooks/pre-commit scripts/verify-commit
+# Or used to verify changes between two commits
+#  $ verify-commit HEAD~2 HEAD
+
+
+# Determine if we need to check A-B or just cached changes
+if [ "$#" == 2 ]; then
+	DIFF_ARGS="$1 $2"
+	CAN_ACCEPT=false
+elif [ "$#" == 0 ]; then
+	DIFF_ARGS="--cached"
+	CAN_ACCEPT=true
+else
+	echo "Unrecognised arguments"
+	exit 1
+fi
+
+CLANG_DIFF=$(git diff ${DIFF_ARGS} -U0 | clang-format-diff -p1)
+WARNED=""
+
+# Check the diff and warn if there is anything that doesn't match the style
+if [ -n "$CLANG_DIFF" ]; then
+	echo "Source does not match expected clang-format"
+	echo "$CLANG_DIFF"
+	WARNED="1"
+fi
+
+# Allow the user to override when running as a hook
+if [ -n "$WARNED" ]; then
+	echo "Warnings detected"
+	if [ "$CAN_ACCEPT" = true ]; then
+		read -p "Are you sure you want to commit? [Y/n] " -n 1 -r
+		echo    # (optional) move to a new line
+		if [[ ! $REPLY =~ ^[Yy]+$ ]]; then
+			exit 1
+		fi
+	else
+		exit 1
+	fi
+fi