Trace methods by call chain?

Instead of specifying one method to trace, would it be useful to trace that method and all the methods that it calls? Maybe add a `--depth` option: "trace the methods that the marked method calls, within the same file, up to the given depth."

The issue proposes tracing a marked method's same-file call chain with a configurable --depth option, but names no files, tests, or entry points. Begin by locating the existing method-tracing implementation and determine how call depth and same-file boundaries should be defined; done means the option traces the intended callees up to the requested depth.

Written by the indexing model from the issue text.