This could be an enhancement that make administration less dependent on the web interface:

allow appending new SSH keys to .ssh/authorized_keys in the "setup" branch of a site at Branchable via git+ssh (by the admin only--for security, perhaps; i.e., keep track which SSH keys belong to the owner of the site by some means, if this is important).

Now this is forbidden: after appending a new SSH key, the attempt to upload the commit fails:

$ git push -v
Pushing to ssh://b-pay-assistant@pay-assistant.branchable.com/
Enter passphrase for key '/home/imz/.ssh/id_rsa': 
Counting objects: 7, done.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (4/4), 1.04 KiB, done.
Total 4 (delta 0), reused 0 (delta 0)
remote: error: rejecting change to setup branch: modification of files other than ikiwiki.setup is not allowed        
remote: 
remote: error: hook declined to update refs/heads/setup        
To ssh://b-pay-assistant@pay-assistant.branchable.com/
! [remote rejected] setup -> setup (hook declined)
error: failed to push some refs to 'ssh://b-pay-assistant@pay-assistant.branchable.com/'
$ 

Of course, this doesn't seem to be a very essential enhancement, but some conevnience for those who prefer git and command-line and files to the web interface. -- Ivan Z.