Improve deprecation warning

Turns out GitHub doesn't forward @master to @main

README.md

@@ -78,3 +78,13 @@ If you only want to add this prefix on certain builds, you can [include addition
 ```
 
 This will add the prefix `xvfb-run` to all builds where the `os` is `ubuntu-latest`.
+
+
+### Registry flavor preference
+
+This actions defines (and exports for subsequent steps of the workflow) the
+environmental variable `JULIA_PKG_SERVER_REGISTRY_PREFERENCE=eager` unless it
+is already set. If you want another registry flavor (i.e. `conservative`) this
+should be defined in the `env:` section of the relevant workflow or step. See
+[Registry flavors](https://pkgdocs.julialang.org/dev/registries/#Registry-flavors)
+for more information.

action.yml

@@ -36,6 +36,14 @@ inputs:
 runs:
   using: 'composite'
   steps:
+    - name: 'DEPRECATION WARNING: julia-actions/julia-runtest@master will no longer receive updates and will start to error in the future. Please use version tags like julia-actions/julia-runtest@v1 or commit SHAs in your workflows!'
+      run: |
+        echo "::warning title=DEPRECATION WARNING::julia-actions/julia-runtest@master will no longer receive updates and will start to error in the future. Please use version tags like julia-actions/julia-runtest@v1 or commit SHAs in your workflows!"
+        echo "# :warning: DEPRECATION WARNING :warning: julia-actions/julia-runtest@master will no longer receive updates and will start to error in the future. Please use version tags like julia-actions/julia-runtest@v1 or commit SHAs in your workflows!" >> $GITHUB_STEP_SUMMARY
+      shell: bash
+    - name: Set and export registry flavor preference
+      run: echo "JULIA_PKG_SERVER_REGISTRY_PREFERENCE=${JULIA_PKG_SERVER_REGISTRY_PREFERENCE:-eager}" >> ${GITHUB_ENV}
+      shell: bash
     - name: Install dependencies in their own (shared) environment
       run: |
         if VERSION > v"1.8pre"
@@ -45,8 +53,6 @@ runs:
         end
       shell: julia --color=yes {0}
       if: inputs.annotate == 'true'
-      env:
-        JULIA_PKG_SERVER_REGISTRY_PREFERENCE: "${{ env.JULIA_PKG_SERVER_REGISTRY_PREFERENCE == '' && 'eager' || env.JULIA_PKG_SERVER_REGISTRY_PREFERENCE }}"
     - run: |
         # The Julia command that will be executed
         julia_cmd=( julia --color=yes --depwarn=${{ inputs.depwarn }} --inline=${{ inputs.inline }} --project=${{ inputs.project }} -e 'include(joinpath(ENV["GITHUB_ACTION_PATH"], "test_harness.jl"))' )
@@ -64,4 +70,3 @@ runs:
         COVERAGE: ${{ inputs.coverage }}
         FORCE_LATEST_COMPATIBLE_VERSION: ${{ inputs.force_latest_compatible_version }}
         CHECK_BOUNDS: ${{ inputs.check_bounds }}
-        JULIA_PKG_SERVER_REGISTRY_PREFERENCE: "${{ env.JULIA_PKG_SERVER_REGISTRY_PREFERENCE == '' && 'eager' || env.JULIA_PKG_SERVER_REGISTRY_PREFERENCE }}"