test(agent/agentssh): use fish shell compatible exit status checking (#18824)

ethanndickson · web-flow · commit c1b2304d183a · 2025-07-10T19:50:30.000+10:00
This (week-old) test was failing in my workspace because I use fish shell. 
I really do not like that Fish shell does not support `$?`, but I also do like Fish shell! We have a few people at Coder who use it who would appreciate this change.
diff --git a/agent/agentssh/agentssh_test.go b/agent/agentssh/agentssh_test.go
@@ -453,7 +453,7 @@ func TestSSHServer_ClosesStdin(t *testing.T) {
 	// exit code 1 if it hits EOF, which is what we want to test.
 	cmdErrCh := make(chan error, 1)
 	go func() {
-		cmdErrCh <- sess.Start(fmt.Sprintf("echo started; read; echo \"read exit code: $?\" > %s", filePath))
+		cmdErrCh <- sess.Start(fmt.Sprintf(`echo started; echo "read exit code: $(read && echo 0 || echo 1)" > %s`, filePath))
 	}()
 
 	cmdErr := testutil.RequireReceive(ctx, t, cmdErrCh)
