We were looking these up on each request to an issue page, because the form is
pre-filled, as is the template dropdown. That was unnecessary: we could just
treat these as 'special' repository files (like the rendered README) and cache
them in Redis until they change on a push.

The basename appears to have been a holdover from the past - it doesn't look
necessary now. Some of the regexes were unanchored on one side, so explicitly
ensure that they only match the root.

Apart from that, this means that pushing to foo/README.md will no longer
invalidate the main README cache for a project.

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

When no fork network exists for the source projects, we create a new
one with the correct source

The fork network will keep track of the root project as long as it's
present.

In GitLab EE, a GitLab instance can be read-only (e.g. when it's a Geo
secondary node). But in GitLab CE it also might be useful to have the
"read-only" idea around. So port it back to GitLab CE.

Also having the principle of read-only in GitLab CE would hopefully
lead to less errors introduced, doing write operations when there
aren't allowed for read-only calls.

Closes gitlab-org/gitlab-ce#37534.

We used to include the first and last name of the user, but !6624 modified
this to include only the username. Let's compromise and add both in the form
of `First Last (username)`.

Closes #38865

Additionally we're delegating missing method calls on GpgKeySubkey to
GpgKey since most of the info required when verifying a signature is
found on GpgKey which is the parent of GpgKeySubkey

The content returned by #key is important when veryfying the signature,
so given we don't want to repeat it in the database for GPG subkeys we
need to delegate it to the parent.

Signed-off-by: Rémy Coutable <remy@rymai.me>