Who has been working with client GitKraken as GIT, you will know that authentication required?
For the application, log in with: firstemail@outlook.com<
Adding additional information, as this just bit me today.
The login credentials it is requesting are from visualstudio.com (VSTS). Authenticating to VSTS through GitKraken request a personal access token (PAT) or git credentials (as mentioned by user Roet). Personal access tokens can be created through the VSTS web portal, as described in this blog post (no relation): Personal Access Tokens in VSTS