I agree with RjOllos that the trac-github plugin is the best way to accomplish the integration that you want. One of the main features of the plugin is that it supports "direct changeset TracLinks to GitHub's repository browser." Per the Trac site, TracLinks are a fundamental feature of Trac, because they allow easy hyperlinking between the various entities in the system — such as changesets and commit messages. This sounds like the feature you are looking for to provide links from Trac to revisions in Git.
In version 2.3 of the plugin, it states that they have added "Support webhook signature verification for post commit hooks."
They also provide some nice setup steps which can sometime be lacking with other Trac plugins.