SourceTree doesn't launch External Diff/Merge with Visual Studio 2017

[mdabraham]

I'm having trouble using Visual Studio's vsDiffMerge as the External Diff/Merge Tool in SourceTree.

Possibly relevant info:

• SourceTree version: 3.2.6.35544 
• Windows version: Win 10 1903.18362.356
• Confirmed path to tool: "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer\vsDiffMerge.exe"
• Diff args: "$LOCAL" "$REMOTE" "Source" "Target" //t
• Merge args: "$LOCAL" "$REMOTE" "$BASE" "$MERGED" //m
• Log from Process Viewer when trying to run External Diff:

{
"Command": "git\r\n-c diff.mnemonicprefix=false -c core.quotepath=false --no-optional-locks -c credential.helper= -c credential.helper=\"C:/Users/<username>/AppData/Local/ATLASS~1/SOURCE~1/GIT_EX~1/GIT-CR~1.EXE\" difftool -y --tool=sourcetree --\r\nSQL/<FileName>",
"Directory": "C:\\Users\\<username>\\source\\Bitbucket\\LiveCheck",
"Status": "Finished",
"Duration": "00:00:00.2626937",
"CallerContext": "GetExternalDiffProcess",
"Output": "Skipping command-line '\"C:\\Users\\<username>\\AppData\\Local\\Atlassian\\SourceTree\\git_local\\bin\\..\\usr\\bin\\bash.exe\"'\n('C:\\Users\\username>\\AppData\\Local\\Atlassian\\SourceTree\\git_local\\bin\\..\\usr\\bin\\bash.exe' not found)\nNeed a valid command-line; Edit the string resources accordingly\nfatal: external diff died, stopping at SQL/<FileName>\n"
}

I know that that the Command doesn't look right, but no matter how I adjust my arguments it doesn't change the command sent. Please someone tell me what I'm doing wrong!