First performance-tests added

performance/out/some_script.txt

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+1_000 iterations of _prev_tup in 1.608ms. The main thing we care about is not this little
+private helper though, but PeriodCounter.inc(). Let's test that next.
+
+On testing: I noticed variations of a factor 2 even running these tests only a couple of times. For now I picked the
+slow results for a check in.
+
+

performance/some_script.py

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+import time
+
+from bugsink.period_counter import _prev_tup
+
+
+# this file is the beginning of an approach to getting a handle on performance.
+
+
+class passed_time(object):
+    def __enter__(self):
+        self.t0 = time.time()
+        return self
+
+    def __exit__(self, type, value, traceback):
+        self.elapsed = (time.time() - self.t0) * 1_000  # miliseconds is a good unit for timeing things
+
+
+def print_thoughts_about_prev_tup():
+    v = (2020, 1, 1, 10, 10)
+    with passed_time() as t:
+        for i in range(1_000):
+            v = _prev_tup(v)
+
+    print(f"""1_000 iterations of _prev_tup in {t.elapsed:.3f}ms. The main thing we care about is not this little
+private helper though, but PeriodCounter.inc(). Let's test that next.
+
+On testing: I noticed variations of a factor 2 even running these tests only a couple of times. For now I picked the
+slow results for a check in.
+
+""")
+
+
+print_thoughts_about_prev_tup()