Fix committer typo

Closes #51808

See merge request gitlab-org/gitlab-ce!21899

Even if it doesn’t save lines of code, since people will tend to use
code they’ve seen. And `SafeRequestStore` is safer since you
don’t have to remember to check `RequestStore.active?`.

When displaying the pipelines of a project we now preload the following
data:

1. Authors of the commits that belong to these pipelines
2. The number of warnings per pipeline, which is used by
   Ci::Pipeline#has_warnings?

== Commit Authors

Previously this data was queried for every Commit separately, leading to
20 SQL queries being executed in the worst case. With an average of 3 to
5 milliseconds per SQL query this could result in 100 milliseconds being
spent in _just_ getting Commit authors.

To preload this data Commit#author now uses BatchLoader (through
Commit#lazy_author), and a separate module
Gitlab::Ci::Pipeline::Preloader is used to ensure all authors are loaded
before they are used.

== Number of warnings

This changes Ci::Pipeline#has_warnings? so it supports preloading of the
number of warnings per pipeline. This removes the need for executing a
COUNT(*) query for every pipeline just to see if it has any warnings or
not.

Prior to this change, this was done through unicorn. In theory this
could time out. Workhorse has been sending these raw patches and diffs
for a long time and is stable in doing so.

Added bonus is the fact that `Commit#to_patch` can be removed.

`Commit#to_diff` too, which closes
https://gitlab.com/gitlab-org/gitaly/issues/324

Closes https://gitlab.com/gitlab-org/gitaly/issues/1196

The execution path wasn't clear from the error, but either way this is a
fix.

Closes gitlab-org/gitaly#1115