Run the manifest updater on the lowest supported version. [ci skip]

Author: maleadt

.github/workflows/update_manifest.yml

@@ -9,19 +9,27 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - name: Get Julia compatibility
+        id: julia_compat
+        # NOTE: this requires a julia compat lower-bound with minor version!
+        run : |
+          version=$(grep '^julia = ' Project.toml | grep -o '".*"' | cut -d '"' -f2)
+          echo "::set-output name=version::$version"
       - uses: julia-actions/setup-julia@latest
+        with:
+          version: ${{ steps.julia_compat.outputs.version }}
       - name: Update packages
-        id: update
+        id: pkg_update
         run: |
-          log=$(julia --project -e "using Pkg; Pkg.update()")
+          log=$(julia --project -e 'using Pkg; Pkg.update()')
           log="${log//'%'/'%25'}"
           log="${log//$'\n'/'%0A'}"
           log="${log//$'\r'/'%0D'}"
           echo "::set-output name=log::$log"
       - name: Get status
-        id: status
+        id: pkg_status
         run: |
-          log=$(julia --project -e "using Pkg; Pkg.status(diff=true)")
+          log=$(julia --project -e 'using Pkg; VERSION >= v"1.3" ? Pkg.status(diff=true) : Pkg.status()')
           log="${log//'%'/'%25'}"
           log="${log//$'\n'/'%0A'}"
           log="${log//$'\r'/'%0D'}"
@@ -37,21 +45,21 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
           commit-message: |
             Update dependencies.
-            ${{ steps.status.outputs.log }}
+            ${{ steps.pkg_status.outputs.log }}
           title: Update manifest
           reviewers: maleadt
           body: |
             This pull request updates the manifest for Julia v${{ steps.version.outputs.log }}:
 
             ```
-            ${{ steps.status.outputs.log }}
+            ${{ steps.pkg_status.outputs.log }}
             ```
 
             <details><summary>Click here for the full update log.</summary>
             <p>
 
             ```
-            ${{ steps.update.outputs.log }}
+            ${{ steps.pkg_update.outputs.log }}
             ```
 
             </p>