複数のGitアカウントの鍵を使い分けるパターン

ディレクトリ構成とファイル

$ tree ~/.ssh
~/.ssh
├── github_private
└── github_company

~/.gitconfig

[color]
    ui = true
[includeIf "gitdir:~/misc/dev/git/private/"]
    path = ~/misc/dev/git/private/.gitconfig
[includeIf "gitdir:~/misc/dev/git/company/"]
    path = ~/misc/dev/git/company/.gitconfig

~/misc/dev/git/private/.gitconfig

[user]
    name = private-name
    email = private@example.com
[core]
    sshCommand = ssh -i ~/.ssh/github_private -o IdentitiesOnly=yes -F /dev/null

~/misc/dev/git/company/.gitconfig

[user]
    name = company-name
    email = company@example.com
[core]
    sshCommand = ssh -i ~/.ssh/github_company -o IdentitiesOnly=yes -F /dev/null

として、作業ディレクトリは
~/misc/dev/git/privateと
~/misc/dev/git/companyになり
そこでgit cloneとかすると勝手に鍵を使い分けてくれる