Add git commit message hook to the mystools bundle (#1067)

The message hook validates that the c ommit message follows
the MySensors requirements.
More specifically, it checks that
- Commit message does not exceed a line length of 72 characters
- Commit title start with an uppercase character
- Commit title does not end with a period ('.')

Fixes #672

.mystools/hooks/commit-msg.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+too_long_lines=$(awk 'length>72' $1)
+if [[ ! -z $too_long_lines ]]; then
+	echo "Too long commit message lines:" $too_long_lines
+	has_failed=1
+fi
+
+leading_lowercases=$(awk 'NR==1' $1 | awk '/^[[:lower:][:punct:]]/')
+if [[ ! -z $leading_lowercases ]]; then
+	echo "Leading lowercase in subject:" $leading_lowercases
+	has_failed=1
+fi
+
+trailing_periods=$(awk 'NR==1' $1 | awk '/(\.)$/')
+if [[ ! -z $trailing_periods ]]; then
+	echo "Trailing periods in subject:" $trailing_periods
+	has_failed=1
+fi
+
+if [[ ! -z $has_failed ]]; then
+	echo "Please recommit with a new commit message."
+	exit 1
+fi