unneccessary overwriting warning on FIDO credentials

[robinschwab]

Prerequisites

• Write a descriptive title.
• Make sure you are able to repro it on the latest version
• Search the existing issues.

Steps to reproduce

When I use any FIDO device no matter if out of the box or already programmed I get an overwrite warning when adding new keys. On a new device you might just click away this warning. But on a "hot" device this leads to a lot of insecurity. Will it overwrite an existing key? It is a bad habit to get used to click away warnings.

So the suggestion is not to throw a warning when ssh-keygen does not overwrite anything.

Expected behavior

PS C:\Users\xyz\.ssh> ssh-keygen -t ed25519-sk -O resident
Generating public/private ed25519-sk key pair.
You may need to touch your authenticator to authorize key generation.
Enter file in which to save the key (C:\Users\xyz/.ssh/id_ed25519_sk):

Actual behavior

PS C:\Users\xyz\.ssh> ssh-keygen -t ed25519-sk -O resident
Generating public/private ed25519-sk key pair.
You may need to touch your authenticator to authorize key generation.
A resident key scoped to 'ssh:' with user id 'null' already exists.
Overwrite key in token (y/n)?

Error details

No response

Environment data

PS C:\Users\xyz\.ssh> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.4.1
PSEdition                      Core
GitCommitId                    7.4.1
OS                             Microsoft Windows 10.0.19045
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Version

OpenSSH_for_Windows_9.5p1, LibreSSL 3.8.2

Visuals

No response