This is an initiative to ensure all documentation complies completely
with the Documentation Style Guide section "Documentation is the single
source of truth (SSOT)" according to this epic
https://gitlab.com/groups/gitlab-org/-/epics/1280.
In particular, the changes of this commit touch all files under
doc/install/. Most notably:
- install/redis.md:
Redirect to Redis section of install guide.
- install/pivotal/index.md:
Changed its content to reflect the current status, which is no
longer supported (since 2017!).
- install/google-protobuf.md:
Incorporated inside installation.md under the troubleshooting section.
- install/openshift_and_gitlab.md:
Clarified that this guide is no longer relevant. We might want to
redirect to the Chart docs in the future.
- install/structure.md:
Incorporated inside installation.md under its own section.
- install/kubernetes/index.md:
Redirected to https://docs.gitlab.com/charts
