I added -v option in the ssh command and here’s the output:
#!/bin/bash -eo pipefail
GIT_SSH_COMMAND='ssh -v -i ~/.ssh/id_rsa_<fingerprint>' git clone git@github.com:user/my-app-frontend.git ~/my-app-frontend
Cloning into '/home/circleci/my-app-frontend'...
OpenSSH_7.4p1 Debian-10+deb9u4, OpenSSL 1.0.2l 25 May 2017
debug1: Reading configuration data /home/circleci/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to github.com [192.30.253.112] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/circleci/.ssh/id_rsa_<fingerprint> type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/circleci/.ssh/id_rsa_<fingerprint>-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4p1 Debian-10+deb9u4
debug1: Remote protocol version 2.0, remote software version libssh_0.7.0
debug1: no match: libssh_0.7.0
debug1: Authenticating to github.com:22 as 'git'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256@libssh.org
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ssh-rsa SHA256:<key>
debug1: Host 'github.com' is known and matches the RSA host key.
debug1: Found key in /home/circleci/.ssh/known_hosts:1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key:
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug1: Authentication succeeded (publickey).
Authenticated to github.com ([192.30.253.112]:22).
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: pledge: network
debug1: Sending environment.
debug1: Sending env LANG = C.UTF-8
debug1: Sending command: git-upload-pack 'user/my-app-frontend.git'
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
ERROR: Repository not found.
debug1: channel 0: free: client-session, nchannels 1
debug1: fd 0 clearing O_NONBLOCK
debug1: fd 1 clearing O_NONBLOCK
Transferred: sent 2756, received 1704 bytes, in 0.0 seconds
Bytes per second: sent 64184.2, received 39684.3
debug1: Exit status 1
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
Exited with code 128
When it comes to \ at the end of GIT_SSH_COMMAND line it didn’t work, cause I got:
#!/bin/bash -eo pipefail
GIT_SSH_COMMAND='ssh -v -i ~/.ssh/id_rsa_<fingerprint>'\ git clone git@github.com:user/my-app-frontend.git ~/my-app-frontend
/bin/bash: clone: command not found
Exited with code 127
Exporting GIT_SSH_COMMAND described like here didn’t work either.