[GITEA] Fix panic in `canSoftDeleteContentHistory`

- Backport of #2134
- It's possible that `canSoftDeleteContentHistory` is called without
`ctx.Doer` being set, such as an anonymous user requesting the
`/content-history/detail` endpoint.
- Add a simple condition to always set to `canSoftDelete` to false if an
anonymous user is requesting this, this avoids a panic in the code that
assumes `ctx.Doer` is set.
- Added integration testing.

(cherry picked from commit 0b5db0dcc6)

routers/web/repo/issue_content_history.go

@@ -94,6 +94,8 @@ func canSoftDeleteContentHistory(ctx *context.Context, issue *issues_model.Issue
 	// CanWrite means the doer can manage the issue/PR list
 	if ctx.Repo.IsOwner() || ctx.Repo.CanWriteIssuesOrPulls(issue.IsPull) {
 		canSoftDelete = true
+	} else if ctx.Doer == nil {
+		canSoftDelete = false
 	} else {
 		// for read-only users, they could still post issues or comments,
 		// they should be able to delete the history related to their own issue/comment, a case is:

tests/integration/fixtures/TestGetContentHistory/issue_content_history.yml

@@ -0,0 +1,17 @@
+-
+  id: 1
+  issue_id: 1
+  comment_id: 3
+  edited_unix: 1687612839
+  content_text: Original Text
+  is_first_created: true
+  is_deleted: false
+
+-
+  id: 2
+  issue_id: 1
+  comment_id: 3
+  edited_unix: 1687612840
+  content_text: "meh..." # This has to be consistent with comment.yml
+  is_first_created: false
+  is_deleted: false

tests/integration/issue_test.go

@@ -727,3 +727,55 @@ func TestAbsoluteReferenceURL(t *testing.T) {
 		assert.EqualValues(t, setting.AppURL+"user2/repo1/issues/1#issuecomment-2", referenceURL)
 	})
 }
+
+func TestGetContentHistory(t *testing.T) {
+	defer tests.AddFixtures("tests/integration/fixtures/TestGetContentHistory/")()
+	defer tests.PrepareTestEnv(t)()
+
+	issue := unittest.AssertExistsAndLoadBean(t, &issues_model.Issue{ID: 1})
+	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: issue.RepoID})
+	issueURL := fmt.Sprintf("%s/issues/%d", repo.FullName(), issue.Index)
+	contentHistory := unittest.AssertExistsAndLoadBean(t, &issues_model.ContentHistory{ID: 2, IssueID: issue.ID})
+	contentHistoryURL := fmt.Sprintf("%s/issues/%d/content-history/detail?comment_id=%d&history_id=%d", repo.FullName(), issue.Index, contentHistory.CommentID, contentHistory.ID)
+
+	type contentHistoryResp struct {
+		CanSoftDelete bool `json:"canSoftDelete"`
+		HistoryID     int  `json:"historyId"`
+		PrevHistoryID int  `json:"prevHistoryId"`
+	}
+
+	testCase := func(t *testing.T, session *TestSession, canDelete bool) {
+		t.Helper()
+		contentHistoryURL := contentHistoryURL + "&_csrf=" + GetCSRF(t, session, issueURL)
+
+		req := NewRequest(t, "GET", contentHistoryURL)
+		resp := session.MakeRequest(t, req, http.StatusOK)
+
+		var respJSON contentHistoryResp
+		DecodeJSON(t, resp, &respJSON)
+
+		assert.EqualValues(t, canDelete, respJSON.CanSoftDelete)
+		assert.EqualValues(t, contentHistory.ID, respJSON.HistoryID)
+		assert.EqualValues(t, contentHistory.ID-1, respJSON.PrevHistoryID)
+	}
+
+	t.Run("Anonymous", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+		testCase(t, emptyTestSession(t), false)
+	})
+
+	t.Run("Another user", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+		testCase(t, loginUser(t, "user8"), false)
+	})
+
+	t.Run("Repo owner", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+		testCase(t, loginUser(t, "user2"), true)
+	})
+
+	t.Run("Poster", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+		testCase(t, loginUser(t, "user5"), true)
+	})
+}