ci: Add update of R packages for scheduled jobs

Refs #55

.gitlab-ci.yml

 stages:
+  - update_packages
   - build
   - tests
 
@@ -8,6 +9,15 @@ default:
     - PATH=~/R/sources/R-${R_VERSION}/bin:$PATH
     - rename "s/.${R_VERSION}.t/.t/" airGR_*.tar.gz
 
+.update_packages:
+  stage: update_packages
+  only:
+    refs:
+      - tags
+      - schedules
+  script:
+    - Rscript -e "update.packages(ask=FALSE, repos=\"http://cran.r-project.org\")"
+
 .build:
   stage: build
   script:
@@ -32,6 +42,10 @@ default:
   script:
     - R CMD check --as-cran airGR_*.tar.gz
 
+update_packages_patched:
+  variables:
+    R_VERSION: "patched"
+  extends: .update_packages
 
 build_patched:
   variables:
@@ -48,6 +62,11 @@ check_as_cran_patched:
     R_VERSION: "patched"
   extends: .check_as_cran
 
+update_packages_devel:
+  variables:
+    R_VERSION: "devel"
+  extends: .update_packages
+
 build_devel:
   only:
     refs:
@@ -75,6 +94,11 @@ check_as_cran_devel:
     R_VERSION: "devel"
   extends: .check_as_cran
 
+update_packages_oldrel:
+  variables:
+    R_VERSION: "oldrel"
+  extends: .update_packages
+
 build_oldrel:
   only:
     refs: