unknown configuration key: "ssh_disable_agent"

[mcandre]

When I try to generate a Vagrant box for FreeBSD 11.0-20170510-zfs, packer complains of an unknown configuration key: "ssh_disable_agent". Trace:

$ make 11.0-20170510-zfs 
exec /Applications/Xcode.app/Contents/Developer/usr/bin/make _build PROVIDER=vmware-iso EXTRA_OPTS="" TEMPLATE=11.0-amd64-20170510-zfs.json
`go env GOPATH`/bin/packer build -only=vmware-iso -var boot_wait=35s  11.0-amd64-20170510-zfs.json
vmware-iso output will be in this color.

1 error(s) occurred:

* unknown configuration key: "ssh_disable_agent"
make[1]: *** [_build] Error 1
make: *** [11.0-20170510-zfs] Error 2

Based on https://github.com/hashicorp/packer/issues/3261 , I think that the packer configuration has unfortunately introduced a breaking change, so any projects that want to target the latest version of packer need to use ssh_private_key_file instead.

As a workaround, one can specify an earlier version of packer for installation. For example:

$ cd $GOPATH/src/github.com/hashicorp/packer
$ git checkout -b v1.0.4 v1.0.4
$ go install
$ packer -v
1.0.4