[GITEA] avoid superfluous synchronized pull_request run when opening a PR (#2236)

* Split TestPullRequest out of AddTestPullRequestTask
* Before scheduling the task, AddTestPullRequestTask stores the max
  index of the repository
* When the task runs, it does not take into account pull requests that
  have an index higher than the recorded max index

When AddTestPullRequestTask is called with isSync == true, it is the
direct consequence of a new commit being pushed. Forgejo knows nothing
of this new commit yet. If a PR is created later and its head
references the new commit, it will have an index that is higher and
must not be taken into account. It would be acting and triggering a
notification for a PR based on an event that happened before it
existed.

Refs: https://codeberg.org/forgejo/forgejo/issues/2009
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/2236
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Earl Warren <contact@earl-warren.org>
Co-committed-by: Earl Warren <contact@earl-warren.org>
(cherry picked from commit b3be895a30)

models/issues/issue_index_test.go

@@ -0,0 +1,38 @@
+// Copyright 2024 The Forgejo Authors
+// SPDX-License-Identifier: MIT
+
+package issues_test
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	issues_model "code.gitea.io/gitea/models/issues"
+	repo_model "code.gitea.io/gitea/models/repo"
+	"code.gitea.io/gitea/models/unittest"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetMaxIssueIndexForRepo(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 1})
+
+	maxPR, err := issues_model.GetMaxIssueIndexForRepo(db.DefaultContext, repo.ID)
+	assert.NoError(t, err)
+
+	issue := testCreateIssue(t, repo.ID, repo.OwnerID, "title1", "content1", false)
+	assert.Greater(t, issue.Index, maxPR)
+
+	maxPR, err = issues_model.GetMaxIssueIndexForRepo(db.DefaultContext, repo.ID)
+	assert.NoError(t, err)
+
+	pull := testCreateIssue(t, repo.ID, repo.OwnerID, "title2", "content2", true)
+	assert.Greater(t, pull.Index, maxPR)
+
+	maxPR, err = issues_model.GetMaxIssueIndexForRepo(db.DefaultContext, repo.ID)
+	assert.NoError(t, err)
+
+	assert.Equal(t, maxPR, pull.Index)
+}