feat(diff): Enable commenting on expanded lines in PR diffs (#35662)

Fixes #32257 
/claim #32257

Implemented commenting on unchanged lines in Pull Request diffs, lines
are accessed by expanding the diff preview. Comments also appear in the
"Files Changed" tab on the unchanged lines where they were placed.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/commit.go

@@ -276,20 +276,24 @@ func Diff(ctx *context.Context) {
 	userName := ctx.Repo.Owner.Name
 	repoName := ctx.Repo.Repository.Name
 	commitID := ctx.PathParam("sha")
-	var (
-		gitRepo *git.Repository
-		err     error
-	)
+
+	diffBlobExcerptData := &gitdiff.DiffBlobExcerptData{
+		BaseLink:      ctx.Repo.RepoLink + "/blob_excerpt",
+		DiffStyle:     ctx.FormString("style"),
+		AfterCommitID: commitID,
+	}
+	gitRepo := ctx.Repo.GitRepo
+	var gitRepoStore gitrepo.Repository = ctx.Repo.Repository
 
 	if ctx.Data["PageIsWiki"] != nil {
-		gitRepo, err = gitrepo.OpenRepository(ctx, ctx.Repo.Repository.WikiStorageRepo())
+		var err error
+		gitRepoStore = ctx.Repo.Repository.WikiStorageRepo()
+		gitRepo, err = gitrepo.RepositoryFromRequestContextOrOpen(ctx, gitRepoStore)
 		if err != nil {
 			ctx.ServerError("Repo.GitRepo.GetCommit", err)
 			return
 		}
-		defer gitRepo.Close()
-	} else {
-		gitRepo = ctx.Repo.GitRepo
+		diffBlobExcerptData.BaseLink = ctx.Repo.RepoLink + "/wiki/blob_excerpt"
 	}
 
 	commit, err := gitRepo.GetCommit(commitID)
@@ -324,7 +328,7 @@ func Diff(ctx *context.Context) {
 		ctx.NotFound(err)
 		return
 	}
-	diffShortStat, err := gitdiff.GetDiffShortStat(ctx, ctx.Repo.Repository, gitRepo, "", commitID)
+	diffShortStat, err := gitdiff.GetDiffShortStat(ctx, gitRepoStore, gitRepo, "", commitID)
 	if err != nil {
 		ctx.ServerError("GetDiffShortStat", err)
 		return
@@ -360,6 +364,7 @@ func Diff(ctx *context.Context) {
 	ctx.Data["Title"] = commit.Summary() + " · " + base.ShortSha(commitID)
 	ctx.Data["Commit"] = commit
 	ctx.Data["Diff"] = diff
+	ctx.Data["DiffBlobExcerptData"] = diffBlobExcerptData
 
 	if !fileOnly {
 		diffTree, err := gitdiff.GetDiffTree(ctx, gitRepo, false, parentCommitID, commitID)