feat(pulls): support per-commit review (#39326)

Opening a single commit of a PR let you look, but not review. The Review
button was disabled and there was no way to reach the next or previous
commit. This finishes https://github.com/go-gitea/gitea/pull/37475,
which only reached the head commit.

- Reviews can be submitted from a single commit, a commit range stays
disabled
- A bar above a single-commit diff shows the commit, its position in the
PR and prev/next buttons
- The commit dropdown marks the commits on screen
- Timeline commits open the PR's commit view, commits force-pushed out
of the PR redirect to the repository commit page

Assisted-by: Claude Code (Fable 5.1)
Co-authored-by: bircni <bircni@icloud.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>

tests/integration/pull_diff_test.go

@@ -25,27 +25,51 @@ func TestPullDiff(t *testing.T) {
 	t.Run("CompletePRDiff", func(t *testing.T) {
 		testPullDiffAssertPage(t, "/user2/commitsonpr/pulls/1/files", false, []string{"test1.txt", "test10.txt", "test2.txt", "test3.txt", "test4.txt", "test5.txt", "test6.txt", "test7.txt", "test8.txt", "test9.txt"})
 	})
-	t.Run("SingleCommitPRDiff", func(t *testing.T) {
-		testPullDiffAssertPage(t, "/user2/commitsonpr/pulls/1/commits/c5626fc9eff57eb1bb7b796b01d4d0f2f3f792a2", true, []string{"test3.txt"})
-	})
 	t.Run("CommitRangePRDiff", func(t *testing.T) {
 		testPullDiffAssertPage(t, "/user2/commitsonpr/pulls/1/files/4ca8bcaf27e28504df7bf996819665986b01c847..23576dd018294e476c06e569b6b0f170d0558705", true, []string{"test2.txt", "test3.txt", "test4.txt"})
 	})
-	t.Run("SingleHeadCommitReviewFormAction", testPullDiffSingleHeadCommitReviewFormAction)
+	t.Run("SingleCommit", testPullDiffSingleCommit)
 }
 
-func testPullDiffSingleHeadCommitReviewFormAction(t *testing.T) {
+func testPullDiffSingleCommit(t *testing.T) {
 	session := loginUser(t, "user2")
-	req := NewRequest(t, "GET", "/user2/commitsonpr/pulls/1/commits/1978192d98bb1b65e11c2cf37da854fbf94bffd6")
+	req := NewRequest(t, "GET", "/user2/commitsonpr/pulls/1/commits/c5626fc9eff57eb1bb7b796b01d4d0f2f3f792a2")
 	resp := session.MakeRequest(t, req, http.StatusOK)
 	doc := NewHTMLParser(t, resp.Body)
 
-	btn := doc.Find(".review-box-button")
-	require.Equal(t, 1, btn.Length())
-	assert.False(t, btn.Is("[disabled]"))
-	form := doc.Find(".review-box-panel form")
-	assert.Equal(t, 1, form.Length())
-	assert.Equal(t, "/user2/commitsonpr/pulls/1/files/reviews/submit", form.AttrOr("action", ""))
+	bar := doc.Find("[data-commit-single-index]")
+	require.Equal(t, 1, bar.Length())
+	barText := bar.Text()
+	assert.Contains(t, barText, "test 3")
+	assert.Contains(t, barText, "Sebastian Sauer")
+	assert.Equal(t, "3", bar.AttrOr("data-commit-single-index", ""))
+	assert.Equal(t, "10", bar.AttrOr("data-commit-total-count", ""))
+
+	assert.Contains(t, bar.Find(".js-previous-commit-link").AttrOr("href", ""), "/pulls/1/commits/96cef4a7b72b3c208340ae6f0cf55a93e9077c93")
+	assert.Contains(t, bar.Find(".js-next-commit-link").AttrOr("href", ""), "/pulls/1/commits/23576dd018294e476c06e569b6b0f170d0558705")
+
+	commitSelect := doc.Find("#diff-commit-select")
+	assert.Equal(t, "96cef4a7b72b3c208340ae6f0cf55a93e9077c93", commitSelect.AttrOr("data-before-commit", ""))
+	assert.Equal(t, "c5626fc9eff57eb1bb7b796b01d4d0f2f3f792a2", commitSelect.AttrOr("data-after-commit", ""))
+
+	panel := doc.Find(".review-box-panel form")
+	require.Equal(t, 1, panel.Length())
+	assert.Equal(t, "c5626fc9eff57eb1bb7b796b01d4d0f2f3f792a2", panel.Find(`input[name="commit_id"]`).AttrOr("value", ""))
+
+	req = NewRequest(t, "GET", "/user2/commitsonpr/pulls/1/files/reviews/new_comment")
+	resp = session.MakeRequest(t, req, http.StatusOK)
+	assert.Equal(t, "1978192d98bb1b65e11c2cf37da854fbf94bffd6", NewHTMLParser(t, resp.Body).Find(`input[name="latest_commit_id"]`).AttrOr("value", ""))
+
+	req = NewRequest(t, "GET", "/user2/commitsonpr/pulls/1/commits/4ca8bcaf27e28504df7bf996819665986b01c847")
+	resp = session.MakeRequest(t, req, http.StatusOK)
+	bar = NewHTMLParser(t, resp.Body).Find("[data-commit-single-index]")
+	assert.Equal(t, "1", bar.AttrOr("data-commit-single-index", ""))
+	assert.True(t, bar.Find(".js-previous-commit-link").HasClass("disabled"))
+	assert.False(t, bar.Find(".js-next-commit-link").HasClass("disabled"))
+
+	req = NewRequest(t, "GET", "/user2/commitsonpr/pulls/1/commits/cbff181af4c9c7fee3cf6c106699e07d9a3f54e6")
+	resp = session.MakeRequest(t, req, http.StatusSeeOther)
+	assert.Equal(t, "/user2/commitsonpr/commit/cbff181af4c9c7fee3cf6c106699e07d9a3f54e6", test.RedirectURL(resp))
 }
 
 func testPullDiffAssertPage(t *testing.T, prDiffURL string, reviewBtnDisabled bool, expectedFilenames []string) {