Git use Specified SSH Key

##Use ~/.ssh/config##

Host gitolite-as-alice
  HostName git.company.com
  User git
  IdentityFile /home/whoever/.ssh/id_rsa.alice

Host gitolite-as-bob
  HostName git.company.com
  User git
  IdentityFile /home/whoever/.ssh/id_dsa.bob

Then you just use gitolite-as-alice and gitolite-as-bob instead of the hostname in your URL:

git remote add alice git@gitolite-as-alice:whatever.git
git remote add bob git@gitolite-as-bob:whatever.git

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This way is simple, but every link and every one should add a config.

##Use $GIT_SSH##

$GIT_SSH is an environment variable in git, which can be seen in man git:

GIT_SSH
   If this environment variable is set then git fetch and git push will use **this
   command** instead of ssh when they need to connect to a remote system. The
   $GIT_SSH command will be given exactly two arguments: the username@host (or
   just host) from the URL and the shell command to execute on that remote system.

   To pass options to the program that you want to list in GIT_SSH you will need
   to wrap the program and options into a shell script, then set GIT_SSH to refer
   to the shell script.

   Usually it is easier to configure any desired options through your personal
   .ssh/config file. Please consult your ssh documentation for further details.

write a wapper named ssh-git.sh:

#!/bin/sh

if [ -z "$PKEY" ]; then
    # if PKEY is not specified, run ssh using default keyfile
    ssh "$@"
else
    ssh -i "$PKEY" "$@"
fi

Then :

PKEY=~/.ssh/xxx-id_rsa GIT_SSH=/path/to/ssh-git.sh git pull

and GIT_SSH can be set to a system environment variable and not need to set GIT_SSH every time.

export GIT_SSH=/path/to/ssh-git.sh
PKEY=~/.ssh/xxx-id_rsa git pull

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