Backport #26290 by @Zettat123
Fixes#26270.
Co-Author: @wxiaoguang
Thanks @lunny for providing this solution
As
https://github.com/go-gitea/gitea/issues/26270#issuecomment-1661695151
said, at present we cannot get the names of changed files correctly when
the `OldCommitID` is `EmptySHA`. In this PR, the `GetCommitFilesChanged`
method is added and will be used to get the changed files by commit ID.
References:
- https://stackoverflow.com/a/424142
Co-authored-by: Zettat123 <zettat123@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>