Patch accepted BorgBackup: Modifications to documentation, so to recommend a more secure default setup 
 borgbackup home page
 github issue #8318
 github pull request #8331
 github pull request #8620
 documentation page where change should eventually show up
 Insight:
 openssh server uses a user's posix shell (typically from /etc/password) to execute the remote command through "$SHELL" -c "$COMMAND".