Light revisions to Gitaly touchpoint page

Let's get this work out the door. Light polishing to fix pipeline
errors and some word choices. It's developer documentation and
doesn't need a high gloss.

doc/development/backend/create_source_code_be/gitaly_touch_points.md

+---
+stage: Create
+group: Source Code
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
+---
+
+# Source Code - Gitaly Touch Points
+
+## RPCs
+
+Gitaly is a wrapper around the `git` binary, running in a [Gitaly Cluster](../../../administration/gitaly/index.md). It provides managed access to the file system housing the `git` repositories, via Golang Remote Procedure Calls (RPCs). Other functions are access optimization, caching, and a form of pagination against the file system.
+
+The comprehensive [Beginner's guide to Gitaly contributions](https://gitlab.com/gitlab-org/gitaly/-/blob/master/doc/beginners_guide.md) is focused on making updates to Gitaly, and offers many insights into how to understand the Gitaly code.
+
+All access to Gitaly from other parts of GitLab are through Create: Source Code endpoints:
+
+## The `Commit` model
+
+After a call is made to Gitaly, Git `commit` information is stored in memory. This information is wrapped by the [Ruby `Commit` Model](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/models/commit.rb), which is a wrapper around [`Gitlab::Git::Commit`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/git/commit.rb).
+
+The `Commit` model acts like an ActiveRecord object, but it does not have a PostgreSQL backend. Instead, it maps back to Gitaly RPCs.
+
+## Rugged Patches
+
+Historically in GitLab, access to the server-based `git` repositories was provided through the [rugged](https://github.com/libgit2/rugged) RubyGem, which provides Ruby bindings to `libgit2`. This was further extended by what is termed "Rugged Patches", [a set of extensions to the Rugged library](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/57317). Rugged implementations of some of the most commonly-used RPCs can be [enabled via feature flags](../../gitaly.md#legacy-rugged-code).
+
+Rugged access requires the use of a NFS file system, a direction GitLab is moving away from in favor of Gitaly Cluster. Rugged has been proposed for [deprecation and removal](https://gitlab.com/gitlab-org/gitaly/-/issues/1690). Several large customers are still using NFS, and a specific removal date is not planned at this point.