[PATCH-for-6.0.1 1/2] gitlab: only let pages be published from default branch

[Philippe Mathieu-Daudé]

From: Daniel P. Berrangé <berrange@redhat.com>

GitLab will happily publish pages generated by the latest CI pipeline
from any branch:

https://docs.gitlab.com/ee/user/project/pages/introduction.html

  "Remember that GitLab Pages are by default branch/tag agnostic
   and their deployment relies solely on what you specify in
   .gitlab-ci.yml. You can limit the pages job with the only
   parameter, whenever a new commit is pushed to a branch used
   specifically for your pages."

The current "pages" job is not limited, so it is happily publishing
docs content from any branch/tag in qemu.git that gets pushed to.
This means we're potentially publishing from the "staging" branch
or worse from outdated "stable-NNN" branches

This change restricts it to only publish from the default branch
in the main repository. For contributor forks, however, we allow
it to publish from any branch, since users will have arbitrarily
named topic branches in flight at any time.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210723113051.2792799-1-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit eafadbbbac06a8d72baa976f4d3c42b0e5f8cfc8)
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 .gitlab-ci.yml | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 52d65d6c04f..f8cc67baad9 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -817,6 +817,17 @@ build-tools-and-docs-debian:
 
 # Prepare for GitLab pages deployment. Anything copied into the
 # "public" directory will be deployed to $USER.gitlab.io/$PROJECT
+#
+# GitLab publishes from any branch that triggers a CI pipeline
+#
+# For the main repo we don't want to publish from 'staging'
+# since that content may not be pushed, nor do we wish to
+# publish from 'stable-NNN' branches as that content is outdated.
+# Thus we restrict to just the default branch
+#
+# For contributor forks we want to publish from any repo so
+# that users can see the results of their commits, regardless
+# of what topic branch they're currently using
 pages:
   image: $CI_REGISTRY_IMAGE/qemu/debian-amd64:latest
   stage: test
@@ -835,3 +846,10 @@ pages:
   artifacts:
     paths:
       - public
+  rules:
+    - if: '$CI_PROJECT_NAMESPACE == "qemu-project" && $CI_COMMIT_BRANCH == 
$CI_DEFAULT_BRANCH'
+      when: on_success
+    - if: '$CI_PROJECT_NAMESPACE == "qemu-project"'
+      when: never
+    - if: '$CI_PROJECT_NAMESPACE != "qemu-project"'
+      when: on_success
-- 
2.31.1