Add pre-commit hook with installer

Will enable pep8 once all the problems are gone

hooks/pre-commit

@@ -0,0 +1,34 @@
+#!/bin/sh
+#
+# Simple pre-commit hook to check that there are no errors in the fdroid
+# metadata files.
+
+# Redirect output to stderr.
+exec 1>&2
+
+FILES="fdroid makebuildserver examples/*.py fdroidserver/*.py"
+
+cmd_exists() {
+	command -v $1 1>/dev/null
+}
+
+# For systems that switched to python3, first check for the python2 versions
+if cmd_exists pyflakes-python2; then
+	PYFLAKES=pyflakes-python2
+elif cmd_exists pyflakes; then
+	PYFLAKES=pyflakes
+else
+	echo "pyflakes is not installed!"
+fi
+
+if cmd_exists pep8-python2; then
+	PEP8=pep8-python2
+elif cmd_exists pep8; then
+	PEP8=pep8
+else
+	echo "pep8 is not installed!"
+fi
+
+# If there are python errors or warnings, print them and fail.
+[ -n "$PYFLAKES" ] && $PYFLAKES $FILES
+#[ -n "$PEP8" ] && $PEP8 --ignore=E123,E501 $FILES