git hooks: lokální flake8 a jen když jsou změny

_git_hooks/pre-commit

@@ -3,4 +3,20 @@
 # Git hook script to verify what is about to be committed.
 # Checks that the changes don't introduce new flake8 errors.
 
-git diff --unified=1 --cached HEAD -- '*py' | flake8 --diff
+TMPDIFF=`tempfile`
+FLAKE8="`git rev-parse --show-toplevel`/bin/flake8"
+
+status=0
+
+git diff --unified=1 --cached HEAD -- '*py' > $TMPDIFF
+
+# only do the check when there are some changes to be commited
+# otherwise flake8 would hang waiting for input
+if [ -s $TMPDIFF ] ; then
+    cat $TMPDIFF | $FLAKE8 --diff
+    status=$?
+fi
+
+rm -f $TMPDIFF
+
+exit $status