with_key("/home/christoffer/ssh_keys/theuser") do
  sh("git clone git@github.com:TheUser/TheProject.git")
end

ssh-agent bash -c 'ssh-add /somewhere/yourkey; git clone git@github.com:user/project.git'

ssh-agent $(ssh-add /somewhere/yourkey; git clone git@github.com:user/project.git)

Host            gitserv
    Hostname        remote.server.com
    IdentityFile    ~/.ssh/id_rsa.github
    IdentitiesOnly yes # see NOTES below

git remote add origin git@gitserv:myrepo.git

git push -v origin master

Host github.com
  IdentityFile ~/.ssh/github_rsa

GIT_SSH_COMMAND='ssh -i private_key_file' git clone host:repo.git

#!/bin/bash

ssh -i /path/to/ssh/secret/key $1 $2

GIT_SSH=my_git_ssh_wrapper git clone git@github.com:TheUser/TheProject.git

Host github.com
HostName github.com
IdentityFile /path/to/your/personal/github/private/key
User dandv

Host github-work
HostName github.com
IdentityFile /path/to/your/work/github/private/key
User workuser

#!/bin/bash
ssh -i ~/.ssh/gitkey_rsa "$@"

export GIT_SSH=~/gitwrap.sh

Host (a space separated list of made up aliases you want to use for the host)
    User git
    Hostname (ip or hostname of git server)
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/id_rsa_(the key you want for this repo)

core.sshCommand:

cd /path/to/my/repo
git config core.sshCommand 'ssh -i private_key_file'
# later on
git clone host:repo.git

git config core.sshCommand "ssh -i ~/.ssh/id_rsa_example -F /dev/null"
git pull
git push

Host *
    User git
    Hostname github.com
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/id_rsa_xxx

git -i ~/.ssh/thatuserkey.pem clone thatuser@myserver.com:/git/repo.git

git.sh -i ~/.ssh/thatuserkey.pem clone thatuser@myserver.com:/git/repo.git

#!/bin/bash

# The MIT License (MIT)
# Copyright (c) 2013 Alvin Abad
# https://alvinabad.wordpress.com/2013/03/23/how-to-specify-an-ssh-key-file-with-the-git-command

if [ $# -eq 0 ]; then
    echo "Git wrapper script that can specify an ssh-key file
Usage:
    git.sh -i ssh-key-file git-command
    "
    exit 1
fi

# remove temporary file on exit
trap 'rm -f /tmp/.git_ssh.$$' 0

if [ "$1" = "-i" ]; then
    SSH_KEY=$2; shift; shift
    echo "ssh -i $SSH_KEY $@" > /tmp/.git_ssh.$$
    chmod +x /tmp/.git_ssh.$$
    export GIT_SSH=/tmp/.git_ssh.$$
fi

# in case the git command is repeated
[ "$1" = "git" ] && shift

# Run the git command
git "$@"

bash -c 'eval `ssh-agent`; ssh-add /home/myname/.dotfiles/gitread; ssh-add -L; cd /home/myname/.dotfiles && git pull; kill $SSH_AGENT_PID'