When you clone a repo from inside portable SourceTree, use ..\Repos\ProjectName instead of D:\SourceTreePortable\Repos\ProjectName . This ensures the repo works even if the USB drive letter changes (e.g., from D: to E:).
Atlassian has explicitly stated that a portable version is not planned because Sourcetree is a .NET application that relies on the standard Windows "ClickOnce" installation process. In modern versions like 2.0+, the application often installs directly into the user's profile directory ( AppData ), which can make it appear portable but still requires an initial setup on that specific machine. Unofficial Portable Workarounds sourcetree portable windows