SSH keys with custom names do not work for testing ssh connection and git push

[vladanan]

Select Topic Area

Bug

Body

I had to test ssh connection with github by using this command:

ssh -T -i ~/.ssh/github git@github.com

not as mentioned in docs:

ssh -T git@github.com

because I created ssh key with custom name 'github' and not default one 'id_ed25519'. This is bug because software checks only default names as can be seen in output of:

ssh -vT git@github.com

...
debug1: identity file /home/username/.ssh/id_rsa type -1
debug1: identity file /home/username/.ssh/id_rsa-cert type -1
debug1: identity file /home/username/.ssh/id_ecdsa type -1
debug1: identity file /home/username/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/username/.ssh/id_ecdsa_sk type -1
debug1: identity file /home/username/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /home/username/.ssh/id_ed25519 type -1
debug1: identity file /home/username/.ssh/id_ed25519-cert type -1
debug1: identity file /home/username/.ssh/id_ed25519_sk type -1
debug1: identity file /home/username/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /home/username/.ssh/id_xmss type -1
debug1: identity file /home/username/.ssh/id_xmss-cert type -1
...
...
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Will attempt key: /home/username/.ssh/id_rsa
debug1: Will attempt key: /home/username/.ssh/id_ecdsa
debug1: Will attempt key: /home/username/.ssh/id_ecdsa_sk
debug1: Will attempt key: /home/username/.ssh/id_ed25519
debug1: Will attempt key: /home/username/.ssh/id_ed25519_sk
debug1: Will attempt key: /home/username/.ssh/id_xmss
debug1: Trying private key: /home/username/.ssh/id_rsa
debug1: Trying private key: /home/username/.ssh/id_ecdsa
debug1: Trying private key: /home/username/.ssh/id_ecdsa_sk
debug1: Trying private key: /home/username/.ssh/id_ed25519
debug1: Trying private key: /home/username/.ssh/id_ed25519_sk
debug1: Trying private key: /home/username/.ssh/id_xmss
debug1: No more authentication methods to try.
git@github.com: Permission denied (publickey).

This workaround with 'ssh -T -i ~/.ssh/github git@github.com' does not solve problem with 'git push'. When user switches urls from HTTPS to SSH with:

git remote set-url origin git@github.com:username/reponame.git

'git push' does NOT work if user has custom name for ssh key instead of deafault one so on 'git push' user gets this:

git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

And this is probably because git push uses under the hood come ssh command that uses exclusively default ssh key names and not custom ones and as far as I can see there is no way to make (another) workaround for this.

[github-actions[bot]]

💬 Your Product Feedback Has Been Submitted 🎉

Thank you for taking the time to share your insights with us! Your feedback is invaluable as we build a better GitHub experience for all our users.

Here's what you can expect moving forward ⏩

• Your input will be carefully reviewed and cataloged by members of our product teams. 
  • Due to the high volume of submissions, we may not always be able to provide individual responses.
  • Rest assured, your feedback will help chart our course for product improvements.
• Other users may engage with your post, sharing their own perspectives or experiences. 
• GitHub staff may reach out for further clarification or insight. 
  • We may 'Answer' your discussion if there is a current solution, workaround, or roadmap/changelog post related to the feedback.

Where to look to see what's shipping 👀

• Read the Changelog for real-time updates on the latest GitHub features, enhancements, and calls for feedback.
• Explore our Product Roadmap, which details upcoming major releases and initiatives.

What you can do in the meantime 💻

• Upvote and comment on other user feedback Discussions that resonate with you.
• Add more information at any point! Useful details include: use cases, relevant labels, desired outcomes, and any accompanying screenshots.

As a member of the GitHub community, your participation is essential. While we can't promise that every suggestion will be implemented, we want to emphasize that your feedback is instrumental in guiding our decisions and priorities.

Thank you once again for your contribution to making GitHub even better! We're grateful for your ongoing support and collaboration in shaping the future of our platform. ⭐