git clone git@github.com:TheUser/TheProject.git -key "/home/christoffer/ssh_keys/theuser"

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

core.sshCommand:

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

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

export GIT_SSH=~/gitwrap.sh

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

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)

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'

Host gitlab.com
  RSAAuthentication yes
  IdentityFile ~/.ssh/your_private_key_name
  IdentitiesOnly yes

Host my_synology
    Hostname xxxx.synology.me
    IdentityFile ~/.ssh/id_rsa_xxxx
    User myname
    Port xx

git clone my_synology:path/to/repo.git