pylint_check: Let user specify a specific directory to check

For instance, while working on CircuitPython_RGBMatrix, I can just run
    ./pylint_check CircuitPython_RGBMatrix
which gives a much faster turnaround time (a few seconds, rather than minutes
on my laptop) and doesn't show extraneous messages about other code fragments.

When no argument is specified, the script behaves as before, so it does not
affect CI.

Author: jepler

pylint_check

@@ -1,11 +1,14 @@
 #!/bin/bash
 
+PYLINT="`type -p pylint3 2>/dev/null || type -p pylint`"
+
 function find_pyfiles() {
-    for f in $(find . -type f -iname '*.py'); do
+    if [ $# -eq 0 ]; then set -- .; fi
+    for f in $(find "$@" -type f -iname '*.py'); do
         if [ ! -e "$(dirname $f)/.circuitpython.skip" ]; then
             echo "$f"
         fi
     done
 }
 
-find_pyfiles | xargs pylint
+find_pyfiles "$@" | xargs "$PYLINT"