Add testing for the patch system (#8303)

We test actually applying all of our real patches on release branches,
but this adds testing on the master branch of the patch system itself.

It works in basically the same way as our inplace upgrade tests: by
creating a database, and then applying a diff that makes some
synthetic testing changes to the server/compiler.

I (re)discovered some various frustrating limitations of the patch
system
while doing this, but haven't fixed those yet.

Fixes #5804.

.github/workflows.src/tests-inplace.tpl.yml

@@ -1,6 +1,6 @@
 <% from "tests.inc.yml" import build, calc_cache_key, restore_cache -%>
 
-name: Tests of in-place upgrades
+name: Tests of in-place upgrades and patching
 
 on:
   schedule:
@@ -22,7 +22,7 @@ jobs:
         << calc_cache_key()|indent >>
     <%- endcall %>
 
-  test:
+  test-inplace:
     runs-on: ubuntu-latest
     needs: build
     strategy:
@@ -47,12 +47,23 @@ jobs:
       run: |
         ./tests/inplace-testing/test.sh ${{ matrix.flags }} vt ${{ matrix.tests }}
 
+  test-patches:
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+    <<- restore_cache() >>
+
+    - name: Test performing in-place upgrades
+      run: |
+        ./tests/patch-testing/test.sh test-dir -k test_link_on_target_delete -k test_edgeql_select -k test_edgeql_scope -k test_dump
+
   workflow-notifications:
     if: failure() && github.event_name != 'pull_request'
     name: Notify in Slack on failures
     needs:
       - build
-      - test
+      - test-inplace
+      - test-patches
     runs-on: ubuntu-latest
     permissions:
       actions: 'read'

tests/patch-testing/test.sh

@@ -0,0 +1,48 @@
+#!/bin/bash -ex
+
+while [[ $# -gt 0 ]]; do
+  case $1 in
+    --save-tarballs)
+        SAVE_TARBALLS=1
+        shift
+        ;;
+    *)
+        break
+        ;;
+  esac
+done
+
+
+DIR="$1"
+shift
+
+if ! git diff-index --quiet HEAD --; then
+    set +x
+    echo Refusing to run patching upgrade test with dirty git state.
+    echo "(The test makes local modifications.)"
+    exit 1
+fi
+
+make parsers
+
+# Setup the test database
+edb inittestdb -D "$DIR" "$@"
+
+
+if [ "$SAVE_TARBALLS" = 1 ]; then
+    tar cf "$DIR".tar "$DIR"
+fi
+
+
+# Upgrade to the new version
+patch -f -p1 < tests/patch-testing/upgrade.patch
+make parsers
+
+edb server --bootstrap-only --data-dir "$DIR"
+
+if [ "$SAVE_TARBALLS" = 1 ]; then
+    tar cf "$DIR"-upgraded.tar "$DIR"
+fi
+
+# Test!
+edb test --data-dir "$DIR" --use-data-dir-dbs -v "$@"