repo.Blame(path) does not accept folders

Reproduction steps

string relativePath = @"folder\anatherFolder\test.ts"
call repository.Blame(relativePath)
throws exception: "'the path 'folder\anatherFolder\test.ts' does not exist in the given tree"

Expected behavior

accept absolute or relative path
get all Hunks for file in path

Actual behavior

only accepts files in root directory of repository
throws exception: "'the path 'folder\anatherFolder\test.ts' does not exist in the given tree"

Version of LibGit2Sharp (release number or SHA1)

0.25.3

Operating system(s) tested; .NET runtime tested

.NET Core 2.1

從 repository.Blame(path) 入口開始，使用 LibGit2Sharp 0.25.3 和 .NET Core 2.1，透過巢狀路徑 folder\anatherFolder\test.ts 重現該失敗。追蹤路徑的解析方式，然後驗證 Blame 接受資料夾中的絕對路徑和相對路徑，並回傳該檔案的所有 hunk。