Magit connecting to github with alternate ssh key

Question

I have two github accounts – one personal and one for my job. In most of my repos, I use my work account and magit works fine. In a couple personal repos, I have this in .git/config:

sshCommand = ssh -i /my/home/directory/.ssh/personal/id_rsa -F /dev/null

This works well from the command line for things like git push, but when I try to push from magit, I get this error:

ERROR: Permission to <personalaccount>/unified_docs_switcher.git denied to <workaccount>.

Since my work account is mentioned in the error message, it seems like magit's connection to git is ignoring the line in .git/config.

Is there some other config I can add to magit to recognize this?

Is there a different/better solution in magit to using different github accounts?

(Edit: emacs 27.1 on MacOS from here, tested on magit 2.90.1 from melpa-stable and then 20210105.1030 from melpa)

Answer 1

There's a pure Git solution you can use in your global .gitconfig - I use an include.path config for personal stuff by default:

# .gitconfig
# default user email and key
[include]
        path = .gitconfig-personal

and that file contains name, personal email (which is used for SSH and identifying my GitHub account), and GPG key ID:

# .gitconfig-personal
[user]
    name = jidicula
    email = "johanan@forcepush.tech"
    signingkey = "<personalKeyID>"

Then, below that first [include] in my global .gitconfig, I have an includeIf.path work config to use if the repo matches a pattern provided as an argument to includeIf:

# .gitconfig
# When working with Work
[includeIf "gitdir:**/work/**/.git"]
        path = .gitconfig-work

and that file contains name, work email, and work email GPG key ID:

# .gitconfig-work
[user]
        name = jidicula
        email = "johanan@work.email"
        signingkey = "<workKeyID>"

Anything in this second config will overwrite whatever was defined by default - paired with the conditional includeIf, we get path-dependent Git config.

Putting the global .gitconfig all together, we get:

# .gitconfig
# default user email and key
[include]
        path = .gitconfig-personal
# When working with Work
[includeIf "gitdir:**/work/**/.git"]
        path = .gitconfig-work

Then you'd fill .gitconfig-personal and gitconfig-work with your context-specific configs like emails, keys, usernames, pull behaviour, commit message templates, etc.

You can read more about conditional includes here.