Try
ssh -v git@bitbucket.org -i /path/to/abc
Man Page says
-i identity_file Selects a file from which the identity (private key) for public
key authentication is read. The default is ~/.ssh/identity for protocol version 1,
and ~/.ssh/id_dsa, ~/.ssh/id_ecdsa and ~/.ssh/id_rsa for protocol version 2.
Identity files may also be specified on a per-host basis in the configuration
file. It is possible to have multiple -i options (and multiple identities
specified in configuration files). ssh will also try to load certificate
information from the filename obtained by appending -cert.pub to identity
filenames.