fix(migrations): preserve SHA-256 pull request commit IDs (#39343)

* Fixes #39339

---------

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

modules/git/repo_commit.go

@@ -203,8 +203,8 @@ func (repo *Repository) searchCommits(ctx context.Context, id ObjectID, opts Sea
 	// if there are any keywords (ie not committer:, author:, time:)
 	// then let's iterate over them
 	for _, v := range opts.Keywords {
-		// ignore anything not matching a valid sha pattern
-		if id.Type().IsValid(v) {
+		// ignore anything not matching a valid sha pattern (TODO: the legacy min-length is pretty small, is it right or fine?)
+		if IsStringValidObjectID(id.Type(), v, 4) {
 			// create new git log command with 1 commit limit
 			hashCmd := gitcmd.NewCommand("log", "-1", prettyLogFormat)
 			// add previous arguments except for --grep and --all