Improve caching and fix concurrent CI builds

.gitlab-ci.yml

@@ -3,6 +3,15 @@ stages:
   - docs
   - deploy
 
+variables:
+  GIT_CLONE_PATH: $CI_BUILDS_DIR/$CI_CONCURRENT_ID/$CI_PROJECT_PATH
+  JULIA_DEPOT_PATH: "$CI_PROJECT_DIR/.julia"
+
+cache:
+  paths:
+    - $JULIA_DEPOT_PATH
+  key: "$CI_JOB_NAME-$CI_COMMIT_REF_NAME"
+
 before_script:
   # workaround for https://github.com/JuliaDocs/Documenter.jl/issues/686
   - apt-get -qq update; apt-get -y install git
@@ -40,8 +49,6 @@ Julia 1.8:
   extends:
     - .script
     - .coverage
-  cache:
-    key: "$CI_JOB_NAME-$CI_COMMIT_REF_NAME"
 
 Julia 1.9:
   image: docker.km3net.de/base/julia:1.9
@@ -49,9 +56,6 @@ Julia 1.9:
   extends:
     - .script
     - .coverage
-  cache:
-    key: "$CI_JOB_NAME-$CI_COMMIT_REF_NAME"
-
 
 Julia 1.10:
   image: git.km3net.de:4567/common/dockerfiles/base/julia:1.10
@@ -59,8 +63,6 @@ Julia 1.10:
   extends:
     - .script
     - .coverage
-  cache:
-    key: "$CI_JOB_NAME-$CI_COMMIT_REF_NAME"
 
 Julia 1.11:
   image: git.km3net.de:4567/common/dockerfiles/base/julia:1.11
@@ -68,8 +70,6 @@ Julia 1.11:
   extends:
     - .script
     - .coverage
-  cache:
-    key: "$CI_JOB_NAME-$CI_COMMIT_REF_NAME"
 
 docs:
   image: docker.km3net.de/base/julia:1.9-tex
@@ -90,5 +90,3 @@ docs:
         using NeRCA
         doctest(NeRCA)
         include("docs/make.jl")'
-  cache:
-    key: "$CI_JOB_NAME-$CI_COMMIT_REF_NAME"