test: Update coverage tests to Go 1.20

Go 1.20 finally includes proper support for instrumenting binaries for
coverage. This allows us to drop quite a few hacks and workarounds that
we used for it, and we can now also test exiting cases.

The downside is that coverage tests now require Go 1.20, but it is an
acceptable price to pay for the more accurate results.

Normal integration tests are unchanged.

This patch updates the coverage testing infrastructure to make use of
the new Go 1.20 features.

cmd/dovecot-auth-cli/coverage_test.go

@@ -1,34 +0,0 @@
-// This package is tested externally (see test.sh).
-// However, we need this to do coverage tests.
-//
-// See coverage_test.go for the details, this is the same horrible hack.
-//
-//go:build coveragebin
-// +build coveragebin
-
-package main
-
-import (
-	"os"
-	"os/signal"
-	"syscall"
-	"testing"
-)
-
-func TestRunMain(t *testing.T) {
-	done := make(chan bool)
-
-	signals := make(chan os.Signal, 1)
-	go func() {
-		<-signals
-		done <- true
-	}()
-	signal.Notify(signals, os.Interrupt, os.Kill, syscall.SIGTERM)
-
-	go func() {
-		main()
-		done <- true
-	}()
-
-	<-done
-}

cmd/dovecot-auth-cli/coverage_wrapper

@@ -1,7 +0,0 @@
-#!/bin/bash
-#
-# Wrapper for dovecot-auth-cli to run when we build it in coverage mode.
-
-exec ./dovecot-auth-cli.test -test.run ^TestRunMain$ \
-	-test.coverprofile="$COVER_DIR/test-`date +%s.%N`.out" \
-	"$@"

cmd/dovecot-auth-cli/test.sh

@@ -8,15 +8,13 @@ init
 # Build the binary once, so we can use it and launch it in chamuyero scripts.
 # Otherwise, we not only spend time rebuilding it over and over, but also "go
 # run" masks the exit code, which is something we care about.
-# shellcheck disable=SC2086
-if [ "${COVER_DIR}" != "" ]; then
-	go test -covermode=count -coverpkg=../../... -c \
-		$GOFLAGS -tags="coveragebin $GOTAGS"
-	cp coverage_wrapper dovecot-auth-cli
-else
-	go build $GOFLAGS -tags="$GOTAGS" dovecot-auth-cli.go
+if [ "${GOCOVERDIR}" != "" ]; then
+	GOFLAGS="-cover -covermode=count -o dovecot-auth-cli $GOFLAGS"
 fi
 
+# shellcheck disable=SC2086
+go build $GOFLAGS -tags="$GOTAGS" .
+
 if ! ./dovecot-auth-cli lalala 2>&1 | grep -q "invalid arguments"; then
 	echo "cli worked with invalid arguments"
 	exit 1