Make ./mk/run-test.sh work by itself; add mk/debug-test.sh

First, logic is consolidated in the shell script instead of being spread
between them and makefiles. That makes understanding what is going on a
little easier.

This would not be super interesting by itself, but it gives us a way to
debug tests more easily. *That* in turn I hope is much more compelling.
See the updated manual for details.

Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
Co-authored-by: Eelco Dolstra <edolstra@gmail.com>
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>

mk/run-test.sh

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+
+set -u
+
+red=""
+green=""
+yellow=""
+normal=""
+
+test=$1
+
+dir="$(dirname "${BASH_SOURCE[0]}")"
+source "$dir/common-test.sh"
+
+post_run_msg="ran test $test..."
+if [ -t 1 ]; then
+    red=""
+    green=""
+    yellow=""
+    normal=""
+fi
+
+run_test () {
+    (init_test 2>/dev/null > /dev/null)
+    log="$(run_test_proper 2>&1)"
+    status=$?
+}
+
+run_test
+
+# Hack: Retry the test if it fails with “unexpected EOF reading a line” as these
+# appear randomly without anyone knowing why.
+# See https://github.com/NixOS/nix/issues/3605 for more info
+if [[ $status -ne 0 && $status -ne 99 && \
+    "$(uname)" == "Darwin" && \
+    "$log" =~ "unexpected EOF reading a line" \
+]]; then
+    echo "$post_run_msg [${yellow}FAIL$normal] (possibly flaky, so will be retried)"
+    echo "$log" | sed 's/^/    /'
+    run_test
+fi
+
+if [ $status -eq 0 ]; then
+  echo "$post_run_msg [${green}PASS$normal]"
+elif [ $status -eq 99 ]; then
+  echo "$post_run_msg [${yellow}SKIP$normal]"
+else
+  echo "$post_run_msg [${red}FAIL$normal]"
+  echo "$log" | sed 's/^/    /'
+  exit "$status"
+fi