create and add ssh based git deploy key

create_use_git_deploy_key.md

Guide to create and use ssh key based git deployment

1. Generate key with ssh-keygen, as path enter the same as suggested with a different filename of 'git'
2. run sudo nano ~/.ssh/config and add contents like

# add bitbucket deployment key to identity file
Host bitbucket.org
    User git
    IdentityFile ~/.ssh/git

3. Correct the permissions of the file if it is the first time being used to chmod 600 ~/.ssh/config and sudo chown currentUserName:currentUserGroup ~/.ssh/config
4. dump public key to console with cat ~/.ssh/git.pub
5. copy this key into the bitbucket/github add keys input

Done!