Avast File Shield started blocking access to Sourcetree today (1 November 2019). It says Sourcetree is infected with MacOS:Downloader-X [Drp]. I have not found any information about this virus on the web.
My computer has Avast Security version 14.2 (a3145f33d364) with virus definitions 19110100.
My SourceTree version is 4.0, modified on October 31, 2019 at 2:30 PM.