Update example script (#4)

This is based on some discussion we recently had in SciML, see SciML/MuladdMacro.jl#26 and SciML/MuladdMacro.jl#29

README.md

@@ -1,57 +1,66 @@
 # julia-invalidations
-Uses [`SnoopCompile.@snoopr`](https://timholy.github.io/SnoopCompile.jl/stable/snoopr/) to evaluate number of invalidations caused by `using Package` or a provided script
+Uses [`SnoopCompile.@snoopr`](https://timholy.github.io/SnoopCompile.jl/stable/snoopr/)
+to evaluate number of invalidations caused by `using Package` or a provided script
 
 
 ## Usage
 
 This is a composite github action, that can be inserted into a github action on the target repo to evaluate number of invalidations
 
-For instance, the example below will evaluate number of invalidations that branch/PR has vs. master, and fail if the number increases. Both runs happen on the same julia nightly, so that the comparison in # invalidations is less sensitive to changes in base.
+For instance, the example below will evaluate number of invalidations that branch/PR has vs. the default branch, and fail if the number increases.
+Both runs happen on the same julia version, so that the comparison in # invalidations is less sensitive to changes in Julia.
 
-- Create an action file in the desired repo. i.e. `.github/workflows/InvalidationFlagger.yml`
+- Create an action file in the desired repo. i.e. `.github/workflows/Invalidations.yml`
 
 ```
 name: Invalidations
-on: [push, pull_request]
+
+on:
+  pull_request:
+
+concurrency:
+  # Skip intermediate builds: always.
+  # Cancel intermediate builds: always.
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   evaluate:
+    # Only run on PRs to the default branch.
+    # In the PR trigger above branches can be specified only explicitly whereas this check should work for master, main, or any other default branch
+    if: github.base_ref == github.event.repository.default_branch
     runs-on: ubuntu-latest
     steps:
     - uses: julia-actions/setup-julia@v1
       with:
-        version: 'nightly'
-    - uses: actions/checkout@v2
-    - uses: julia-actions/julia-buildpkg@latest
+        version: '1'
+    - uses: actions/checkout@v3
+    - uses: julia-actions/julia-buildpkg@v1
     - uses: julia-actions/julia-invalidations@v1
       id: invs_pr
-    
-    - uses: actions/checkout@v2
+
+    - uses: actions/checkout@v3
       with:
-        ref: 'master'
-    - uses: julia-actions/julia-buildpkg@latest
+        ref: ${{ github.event.repository.default_branch }}
+    - uses: julia-actions/julia-buildpkg@v1
     - uses: julia-actions/julia-invalidations@v1
-      id: invs_master
+      id: invs_default
     
     - name: Report invalidation counts
       run: |
-        echo "Invalidations on master: ${{ steps.invs_master.outputs.total }} (${{ steps.invs_master.outputs.deps }} via deps)"
-        echo "This branch: ${{ steps.invs_pr.outputs.total }} (${{ steps.invs_pr.outputs.deps }} via deps)"
-      shell: bash
-    - name: PR doesn't increase number of invalidations
-      run: |
-        if (( ${{ steps.invs_pr.outputs.total }} > ${{ steps.invs_master.outputs.total }} )); then
-            exit 1
-        fi
-      shell: bash
+        echo "Invalidations on default branch: ${{ steps.invs_default.outputs.total }} (${{ steps.invs_default.outputs.deps }} via deps)" >> $GITHUB_STEP_SUMMARY
+        echo "This branch: ${{ steps.invs_pr.outputs.total }} (${{ steps.invs_pr.outputs.deps }} via deps)" >> $GITHUB_STEP_SUMMARY
+    - name: Check if the PR does increase number of invalidations
+      if: steps.invs_pr.outputs.total > steps.invs_default.outputs.total
+      run: exit 1
 ```
 
 By default, the action will evaluate `using Package` where `Package` is the name of the julia repo that the action runs on.
 A custom script can be provided by passing `test_script`. Note that both runs should be given the same script
 
 i.e.
 ```
-- uses: julia-actions/julia-invalidations@master
+- uses: julia-actions/julia-invalidations@v1
   id: invs_pr
   with:
     test_script: 'using Package; Package.foo(1)'