Clarify context.go somewhat

in preparation to support parsing a predefined list of Blueprints files

Bug: 64363847
Test: m -j
Change-Id: I98cc98dc17ecaf69b95272d32cd83adbdb0e8c5b
diff --git a/context_test.go b/context_test.go
index b9fb913..1cc051d 100644
--- a/context_test.go
+++ b/context_test.go
@@ -96,7 +96,7 @@
 		}
 	`)
 
-	_, _, errs := ctx.parse(".", "Blueprint", r, nil)
+	_, _, errs := ctx.parseOne(".", "Blueprint", r, nil)
 	if len(errs) > 0 {
 		t.Errorf("unexpected parse errors:")
 		for _, err := range errs {