SSH signing doesn't work

The problem

I have an SSH key tied to my Git configuration. This key works fine when I do a git commit -S -m through Git Bash, but when I do it through GitHub Desktop, I get the following error:

error: Load key “C:\Users\[username]\AppData\Local\Temp/.git_signing_key_tmp[changing string]”: invalid format? fatal: failed to write commit object

Release version

3.0.8

Operating system

Windows 10

Steps to reproduce the behavior

1. Add an SSH key for signing as shown in this GitHub guide
2. Try doing a commit with GitHub Desktop

Log files

2022-09-16.desktop.production.log 2022-09-17.desktop.production.log

Screenshots

Additional context

On my Mac, I don’t get an error when I use my SSH key there. UPDATE 20/09/22: Doesn’t work on a Mac either!

[jblsk]

I have the same behaviour on MacOs Ventura in terminal. Clearly, the path in error message is constructed wrong, as there is duplicated slash after the TMPDIR env. variable:

% git commit -S --amend                                   
error: Load key "/var/folders/x0/2d98rx897cnfgb1q9chxfq4c0000gp/T//.git_signing_key_tmpnM7iuw": invalid format?

fatal: failed to write commit object
% echo error: Load key '"'$TMPDIR
error: Load key "/var/folders/x0/2d98rx897cnfgb1q9chxfq4c0000gp/T/

The key itself is in place:

% ls -a $TMPDIR | grep .git_signing_key_tmpnM7iuw 
.git_signing_key_tmpnM7iuw

but the path to it it the error message on top is wrong.

[applecuckoo]

Alright, filed a bug on the Git mailing list (linked here) about this bug.