Demote some log lines to DEBUG.

Now that we support log line filtering (as of 0090c063) it's good to be
a bit more fussy about what log levels are assigned to different things.

Here we make a few things that are implementation details log as DEBUG,
and prevent spurious errors from EvalValidateCount where it was returning
an empty EvalValidateError rather than nil when everything was okay.

config_unix.go

@@ -33,7 +33,7 @@ func configDir() (string, error) {
 func homeDir() (string, error) {
 	// First prefer the HOME environmental variable
 	if home := os.Getenv("HOME"); home != "" {
-		log.Printf("Detected home directory from env var: %s", home)
+		log.Printf("[DEBUG] Detected home directory from env var: %s", home)
 		return home, nil
 	}
 

plugin/client.go

@@ -88,7 +88,7 @@ func CleanupClients() {
 		}(client)
 	}
 
-	log.Println("waiting for all plugin processes to complete...")
+	log.Println("[DEBUG] waiting for all plugin processes to complete...")
 	wg.Wait()
 }
 
@@ -326,7 +326,7 @@ func (c *Client) logStderr(r io.Reader) {
 			c.config.Stderr.Write([]byte(line))
 
 			line = strings.TrimRightFunc(line, unicode.IsSpace)
-			log.Printf("%s: %s", filepath.Base(c.config.Cmd.Path), line)
+			log.Printf("[DEBUG] %s: %s", filepath.Base(c.config.Cmd.Path), line)
 		}
 
 		if err == io.EOF {

terraform/context.go

@@ -513,7 +513,7 @@ func (c *Context) releaseRun(ch chan<- struct{}) {
 func (c *Context) walk(
 	graph *Graph, operation walkOperation) (*ContextGraphWalker, error) {
 	// Walk the graph
-	log.Printf("[INFO] Starting graph walk: %s", operation.String())
+	log.Printf("[DEBUG] Starting graph walk: %s", operation.String())
 	walker := &ContextGraphWalker{Context: c, Operation: operation}
 	return walker, graph.Walk(walker)
 }

terraform/eval_validate.go

@@ -49,9 +49,12 @@ func (n *EvalValidateCount) Eval(ctx EvalContext) (interface{}, error) {
 	}
 
 RETURN:
-	return nil, &EvalValidateError{
-		Errors: errs,
+	if len(errs) != 0 {
+		err = &EvalValidateError{
+			Errors: errs,
+		}
 	}
+	return nil, err
 }
 
 // EvalValidateProvider is an EvalNode implementation that validates