Add a deploy phase to the CI that tags the latest nightly pipeline if it passes.

.gitlab-ci.yml

@@ -11,6 +11,7 @@ stages:
   - checkformat
   - build
   - test
+  - deploy
 
 variables:
   # CMake build directory.
@@ -29,3 +30,4 @@ include:
   - "/ci/build.windows.gitlab-ci.yml"
   - "/ci/test.linux.gitlab-ci.yml"
   - "/ci/test.windows.gitlab-ci.yml"
+  - "/ci/deploy.gitlab-ci.yml"

ci/deploy.gitlab-ci.yml

@@ -0,0 +1,12 @@
+ # Push a nightly tag if the pipeline succeeded.
+deploy:tag:
+  stage: deploy
+  script:
+    - git tag nightly master
+    - git push https://sillyprof:$EIGEN_CI_ACCESS_TOKEN@gitlab.com/libeigen/eigen.git master tag nightly
+  tags:
+    - linux
+    - eigen-runner
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "schedule" && $CI_PROJECT_NAMESPACE == "libeigen"
+    - if: $CI_PIPELINE_SOURCE == "web" && $CI_PROJECT_NAMESPACE == "libeigen"