If you want to use multiple GitHub accounts, and have your ssh keys stored in 1Password, the environment variable GIT_SSH_COMMAND can be used as an alternative to modify your ~/.ssh/config file

For example if you need to use key1 for project1 define it like this:

export GIT_SSH_COMMAND="ssh -i ~/.ssh/key1.pub -F none"

you can add it to your .envrc and make it global for all projects within a directory.

The option -F none or -F /dev/null makes that no configuration file will be read.

If you then do:

ssh -T [email protected]

It will use the key from user key1 without the need to modify to changte the git URL.