Sourcetree does not convert the backslashes of the path where the new subtree should be added to slashes, see this example:
$ git -c diff.mnemonicprefix=false -c core.quotepath=false subtree add -P Applications\Windows\KeyBoxControl\ProjectRef erences\nagios-nsca-client https://user@server/stash/scm/ac/nagios-nsca-client.git master git fetch https://user@server/stash/scm/ac/nagios-nsca-client.git master From https://server/stash/scm/ac/nagios-nsca-client * branch master -> FETCH_HEAD Added dir 'ApplicationsWindowsKeyBoxControlProjectReferencesnagios-nsca-client'
As you can see the path of the subtree has been changed to one single directory because sourcetree sends the wrong path format in the command