ci: shard tests and reduce redundant work (#37618)

Critical path ~25:42 → ~19:56 (−22%), ~0% CI minutes.

- `test-pgsql` shards 2-way. Branch protection: replace `test-pgsql`
with `test-pgsql-shards (1)` + `test-pgsql-shards (2)`; `test-unit`,
sqlite/mysql/mssql unchanged — pgsql dominates the critical path.
- `test-unit` runs `bindata` then `bindata gogit` sequentially.
cache-seeder pre-warms the race-instrumented test compile cache and the
integration test binary so PR jobs warm-start.
- Cache writes restricted to cache-seeder; PR jobs use
`actions/cache/restore`. Defends against PR cache poisoning and frees
the 10 GB cap from PR churn.
- `go-cache` action: dropped the `cache-name` input. One gobuild cache,
one golangci-lint cache. Seeder lint job restores but doesn't save
gobuild, so only one writer populates it.
- `tools/test-integration.sh` shards the integration binary via
`-test.list`; `TestMain` short-circuits DB init in list mode.

`TestAPILFSNotStarted` / `TestAPILFSLocksNotStarted` switched to
`test.MockVariableValue` — latent `setting.LFS.StartServer` global-state
leak uncovered by sharding.

---
This PR was written with the help of Claude Opus 4.7

---------

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Nicolas <bircni@icloud.com>

.github/workflows/pull-db-tests.yml

@@ -14,10 +14,14 @@ jobs:
   files-changed:
     uses: ./.github/workflows/files-changed.yml
 
-  test-pgsql:
+  test-pgsql-shards:
     if: needs.files-changed.outputs.backend == 'true' || needs.files-changed.outputs.actions == 'true'
     needs: files-changed
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        shard: [1, 2]
     services:
       pgsql:
         image: postgres:14
@@ -48,8 +52,6 @@ jobs:
           check-latest: true
           cache: false
       - uses: ./.github/actions/go-cache
-        with:
-          cache-name: pgsql
       - name: Add hosts to /etc/hosts
         run: '[ -e "/.dockerenv" ] || [ -e "/run/.containerenv" ] || echo "127.0.0.1 pgsql ldap minio" | sudo tee -a /etc/hosts'
       - run: make deps-backend
@@ -57,6 +59,7 @@ jobs:
         env:
           TAGS: bindata
       - name: run migration tests
+        if: matrix.shard == 1
         run: GITEA_TEST_DATABASE=pgsql make test-migration
       - name: run tests
         run: GITEA_TEST_DATABASE=pgsql make test-integration
@@ -66,6 +69,8 @@ jobs:
           GOTEST_FLAGS: -race -timeout=40m
           TAGS: bindata gogit
           TEST_LDAP: 1
+          TEST_SHARD: ${{ matrix.shard }}
+          TEST_TOTAL_SHARDS: ${{ strategy.job-total }}
 
   test-sqlite:
     if: needs.files-changed.outputs.backend == 'true' || needs.files-changed.outputs.actions == 'true'
@@ -79,15 +84,12 @@ jobs:
           check-latest: true
           cache: false
       - uses: ./.github/actions/go-cache
-        with:
-          cache-name: sqlite
       - run: make deps-backend
       - run: make backend
         env:
           TAGS: bindata gogit
           GOEXPERIMENT:
-      - name: run migration tests
-        run: GITEA_TEST_DATABASE=sqlite make test-migration
+      - run: GITEA_TEST_DATABASE=sqlite make test-migration
         env:
           TAGS: bindata gogit
       - name: run tests
@@ -145,28 +147,27 @@ jobs:
           check-latest: true
           cache: false
       - uses: ./.github/actions/go-cache
-        with:
-          cache-name: unit
-          build-cache-rotate: "true"
       - name: Add hosts to /etc/hosts
         run: '[ -e "/.dockerenv" ] || [ -e "/run/.containerenv" ] || echo "127.0.0.1 minio devstoreaccount1.azurite.local mysql elasticsearch meilisearch smtpimap" | sudo tee -a /etc/hosts'
       - run: make deps-backend
-      - run: make backend
+      - run: make generate-go
         env:
           TAGS: bindata
       - name: unit-tests
-        run: make test-backend test-check
+        run: make test-backend
         env:
           GOTEST_FLAGS: -race -timeout=20m
           TAGS: bindata
           GITHUB_READ_TOKEN: ${{ secrets.GITHUB_READ_TOKEN }}
       - name: unit-tests-gogit
-        run: make test-backend test-check
+        run: make test-backend
         env:
           GOTEST_FLAGS: -race -timeout=20m
           TAGS: bindata gogit
           GOEXPERIMENT:
           GITHUB_READ_TOKEN: ${{ secrets.GITHUB_READ_TOKEN }}
+          GITEA_TEST_CI_SKIP_EXTERNAL: true
+      - run: make test-check
 
   test-mysql:
     if: needs.files-changed.outputs.backend == 'true' || needs.files-changed.outputs.actions == 'true'
@@ -205,16 +206,13 @@ jobs:
           check-latest: true
           cache: false
       - uses: ./.github/actions/go-cache
-        with:
-          cache-name: mysql
       - name: Add hosts to /etc/hosts
         run: '[ -e "/.dockerenv" ] || [ -e "/run/.containerenv" ] || echo "127.0.0.1 mysql elasticsearch smtpimap" | sudo tee -a /etc/hosts'
       - run: make deps-backend
       - run: make backend
         env:
           TAGS: bindata
-      - name: run migration tests
-        run: GITEA_TEST_DATABASE=mysql make test-migration
+      - run: GITEA_TEST_DATABASE=mysql make test-migration
       - name: run tests
         run: GITEA_TEST_DATABASE=mysql make test-integration
         env:
@@ -246,8 +244,6 @@ jobs:
           check-latest: true
           cache: false
       - uses: ./.github/actions/go-cache
-        with:
-          cache-name: mssql
       - name: Add hosts to /etc/hosts
         run: '[ -e "/.dockerenv" ] || [ -e "/run/.containerenv" ] || echo "127.0.0.1 mssql devstoreaccount1.azurite.local" | sudo tee -a /etc/hosts'
       - run: make deps-backend