add a script to make it easy to endorse test output

Invoke it on the "out" file and it's moved to the correct "exp" file,
ready to git add & git commit.

tests/endorse.py

@@ -0,0 +1,15 @@
+#!/usr/bin/env python3
+import os
+import sys
+import pathlib
+
+for f in sys.argv[1:]:
+    if not f.endswith(".out"):
+        print(f"{f}:0: Not a .out file")
+        continue
+    p = pathlib.Path(f).stem
+    a, _, b = p.partition("_")
+    print(a, b)
+    p = pathlib.Path(a) / (b + ".exp")
+    print(f"{p}: Updating expected result from {f}")
+    os.rename(f, p)