Describe the actual benefits above and beyond the Git rules.

Bring subheadings more in tune with expected CTRT standards.
Rename subheadings to use present tense instead of gerunds.
Clean up a lot of gunky old wording.

As part of this work, I realized an important part of the forking
instructions were captured on a more generic advanced-settings page.
I've pulled that information back into this page, where it belongs.
That page also had some forking-related troubleshooting info that
also should have been here. I reunited that troubleshooting info
here as well.

We never documented how to configure branch naming defaults for when
users create branches from issues. This required shuffling some
existing content around on the branches page, and documenting some
old OLD tech debt - namely how to create branches, create a branch
in an empty project, and an overarching branch-naming section.

The disqus integration was removed from the docs site,
so these identifiers don't do anything now.

Combine these sections down into one section that adheres to our
content style expectations. Remove several painfully old images. Flow
text back inline for ease of understanding.

Fix instances of naming UI elements that go against our style guide.
Add in hard line wraps. This work should be more fully documented
but let's start here.

For users who need this level of help, we should tell them how to
upload a file.

Flow the information into the main text.
Tighten the language in the cross-links.
Punctuate list items consistently.

Related epic: https://gitlab.com/groups/gitlab-com/-/epics/1940

Because the UI changed.
Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/366082/

Page edits and link updates

Changelog: changed

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/300479

When creating a merge request, the behaviour of the prefilled title and
discription is different than the behaviour of squashed commit messages.

For squashed commit messages, the behaviour is described in the
[docs](https://docs.gitlab.com/ee/user/project/merge_requests/squash_and_merge.html#overview)
as

> Taken from the first multi-line commit message in the merge.

However, for merge requests, the current behavior is to use the branch
name.  This commit sets the prefilled MR title/description to the first
multi-line commit in the MR, if applicable.  Otherwise falling back to
the previous behaviour.

These pages were all part of the Source Code group, but I believe
they should be reassigned to the new(-ish) Code Review group.

Add a preliminary  **(FREE)** badge to the H1 line for each of these
pages. While these badges may not be correct, it will give the PMs an
opportunity to review the badging and correct it if needed.

For the new tier name changes
https://gitlab.com/gitlab-org/technical-writing/-/issues/344

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/291023

The previous URL had two drawbacks:

1. It didn't match what the title was about (`Assignments to DevOps
   Stages and Groups`, and the anchor was `#designated-technical-writers`).
2. It didn't account for the other sections, like development and API
   guidelines.

- Files: merge-requests/*
- Stage: Create
- Group: Source Code

Fix more spelling errors when warranted, and update the exceptions
list when the words are real ones.