gh-36438: .github/workflows/dist.yml: Create release on release tag
    
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We extend our workflow dist.yml, which gets run on every release tag, to
do the following:
- For stable releases (no beta, no rc), when run on sagemath/sage, it
automatically creates a Release. (This saves a few clicks by maintainers
on each release.)
- It uploads the sdist (the 1.2GB file which contains upstream tarballs
for all standard packages) as a Release Asset.
- It uploads the upstream tarballs as Release Assets. They will be used
by the Sage distribution after #36435
Example of the run:
https://github.com/mkoeppe/sage/actions/runs/6464035205/job/17549159925
(where I changed the condition from sagemath/sage to mkoeppe/sage),
leading to the example release
https://github.com/mkoeppe/sage/releases/tag/10.2.beta007

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### 📝 Checklist

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### ⌛ Dependencies

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URL: #36438
Reported by: Matthias Köppe
Reviewer(s): Dima Pasechnik

Author: Release Manager

.github/workflows/dist.yml

@@ -18,9 +18,8 @@ jobs:
 
   release_dist:
 
-    # This job, in contrast to "dist" in ci-macos.yml,
-    # does not use "configure --enable-download-from-upstream-url"
-    # (the default since #32390).
+    # This job first checks whether "configure --enable-download-from-upstream-url"
+    # (the default since #32390) is needed.
     #
     # In this way, we check that all necessary package tarballs
     # have already been uploaded to the Sage server at the time
@@ -37,13 +36,42 @@ jobs:
         run: |
           sudo DEBIAN_FRONTEND=noninteractive apt-get update
           sudo DEBIAN_FRONTEND=noninteractive apt-get install $(build/bin/sage-get-system-packages debian _bootstrap)
-      - name: make dist
+      - name: make dist (--disable-download-from-upstream-url)
         run: |
           ./bootstrap -D && ./configure --disable-download-from-upstream-url && make dist
+        env:
+          MAKE: make -j8
+      - name: make dist (--enable-download-from-upstream-url)
+        if: failure()
+        run: |
+          ./configure && make dist
+        env:
+          MAKE: make -j8
       - uses: actions/upload-artifact@v3
+        if: success() || failure()
+        with:
+          path: |
+            dist/*.tar.gz
+            upstream
+          name: release_dist
+
+  release:
+
+    needs: release_dist
+    runs-on: ubuntu-latest
+    if: (success() || failure()) && github.repository == 'sagemath/sage' && startsWith(github.ref, 'refs/tags/') && !contains(github.ref, 'beta') && !contains(github.ref, 'rc')
+    steps:
+      - uses: actions/download-artifact@v3
         with:
-          path: "dist/*.tar.gz"
           name: release_dist
+      - uses: softprops/action-gh-release@v1
+        with:
+          generate_release_notes: true
+          files: |
+            dist/*
+            upstream/*
+    permissions:
+      contents: write
 
   sdists_for_pypi: