how to sshfs/sftp on boot2docker or docker-toolbox - docker

Question

I work with MacOSX (El Capitan) on a Core2duo processor. I work with Docker, but I can't use native docker and I work with Boot2Docker over VirtualBox.
As filesystem is not share between host and container, I can't work with watch program to auto reload on modification file.
I thought to a solution in editing file over SSHFS. But I can't find out how to do that.
ssh docker#192.168.99.100
Work perfectly with password or with id_rsa key
scp -vvv docker#192.168.99.100:/var/log/*.log ./log
Work also correctly
But I can't succeed with sshsf. Is anybody could help me ?
sshfs -odebug,sshfs_debug,loglevel=debug docker#192.168.99.100:/var/log ./log
SSHFS version 2.5
FUSE library version: 2.9.7
nullpath_ok: 0
nopath: 0
utime_omit_ok: 0
executing <ssh> <-x> <-a> <-oClearAllForwardings=yes> <-ologlevel=debug> <-2> <docker#192.168.99.100> <-s> <sftp>
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug1: /etc/ssh/ssh_config line 56: Applying options for *
debug1: Connecting to 192.168.99.100 [192.168.99.100] port 22.
debug1: Connection established.
debug1: identity file /Users/metzger9/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/metzger9/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/metzger9/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/metzger9/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/metzger9/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/metzger9/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/metzger9/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/metzger9/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.9
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.4
debug1: match: OpenSSH_6.4 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 192.168.99.100:22 as 'docker'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr umac-64-etm#openssh.com none
debug1: kex: client->server aes128-ctr umac-64-etm#openssh.com none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:sY/F5Id4SuRpbOsKcQIGeanTvbibZtsPVV2qGBlSi8A
debug1: Host '192.168.99.100' is known and matches the ECDSA host key.
debug1: Found key in /Users/metzger9/.ssh/known_hosts:7
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /Users/metzger9/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug1: Authentication succeeded (publickey).
Authenticated to 192.168.99.100 ([192.168.99.100]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions#openssh.com
debug1: Entering interactive session.
debug1: Sending environment.
debug1: Sending env LANG = fr_FR.UTF-8
debug1: Sending env LC_CTYPE = en_US.UTF-8
debug1: Sending subsystem: sftp
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_channel_req: channel 0 rtype eow#openssh.com reply 0
debug1: channel 0: free: client-session, nchannels 1
debug1: fd 0 clearing O_NONBLOCK
Transferred: sent 3472, received 2388 bytes, in 0.0 seconds
Bytes per second: sent 122807.4, received 84465.5
debug1: Exit status 127
remote host has disconnected
SOME MORE INFORMATION
It seems that the problem come from sftp program. So trying the command
sftp -vvv docker#192.168.99.100
leads to the same error. Some more googling give me an answer for sftp :
sftp -s /usr/libexec/sftp-server docker#192.168.99.100
which work as expected. Now the question is "How configure the sftp server in the docker engine to be able to use it with sshfs"