- Also makes other minor Markdown fixes that were near the main fixes.

In the administration page for web terminals add a new `Security`
section explaining how the interactive web terminals are secured between
GitLab and gitlab-runner.

This section is under administration instead of
`doc/ci/interactive_web_terminal` because the administrators of the
GitLab instance would be mostly interested in this, whilst
`doc/ci/interactive_web_terminal` are interested in how the feature
works.

closes https://gitlab.com/gitlab-org/gitlab-ce/issues/52681

This adds `project:, file:, ref:` specification support.

Cross link from GitLab CI variable doc too

Add note about running pods and updating secrets without any code change

This rewrites a syntax to allow include of templates.
This also normalises the syntax used by include: feature

Signed-off-by: NTakuya Noguchi <takninnovationresearch@gmail.com>

Signed-off-by: NTakuya Noguchi <takninnovationresearch@gmail.com>

bundler gem has been included in the Docker official Ruby image since 2.1.
Signed-off-by: NTakuya Noguchi <takninnovationresearch@gmail.com>

gitlab-org/gitlab-shell!166 added support for collecting push options
from the environment, and passing them along to the
/internal/post_receive API endpoint.

This change handles the new push_options JSON element in the payload,
and passes them on through to the GitPushService and GitTagPushService
services.

Futhermore, it adds support for the first push option, ci.skip.  With
this change, one can use 'git push -o ci.skip' to skip CI pipe
execution. Note that the pipeline is still created, but in the "skipped"
state, just like with the 'ci skip' commit message text.

Implements #18667

Signed-off-by: NTakuya Noguchi <takninnovationresearch@gmail.com>

Kudos to @eread for feedback!

- Split up refs and kubernetes to their own section
- Use only and except in all headings explicitly
- Document the boolean logic of only and except

- Owners and Maintainers are able to view trigger variable values

This is a documentation change about #15310.

- Adds documentation around viewing trigger variables
- Updates trigger variable values image