Git for Windows update 2.26.1 causing git-remote-keybase.exe to not work?

# Issue

I recently just had Git for Windows update to 2.26.1 and I tried to clone/push to a keybase Git remote from an existing git repo. Kept saying `error: failed to push some refs to ' keybase://private/user/repo_name'`. I also tried creating the symlink to the `git-remote-keybase.exe` in the `C:\Program Files\Git\cmd\` directory.

However, after symlinking it again, and cloning the repo instead of adding it as a remote to the existing repository, I was able to upload the repository to Keybase.

# Version Information

Git for Windows Version

```
C:\Users\preda\Downloads
λ git --version
git version 2.26.1.windows.1
```

Keybase Version

```
C:\Users\preda\Downloads
λ C:\Users\preda\AppData\Local\Keybase\keybase.exe --version
keybase version 5.3.0-20200310141357+4f2689009b
```

Windows Information

```
C:\Users\preda\Downloads
λ Get-ComputerInfo -Property "Windows*"

WindowsBuildLabEx : 18362.1.amd64fre.19h1_release.190318-1202
WindowsCurrentVersion : 6.3
WindowsEditionId : Professional
WindowsInstallationType : Client
WindowsInstallDateFromRegistry : 4/1/2020 12:11:31 AM
WindowsProductId : 00330-80836-81775-AA897
WindowsProductName : Windows 10 Pro
WindowsRegisteredOrganization :
WindowsRegisteredOwner : predatorian3@gmail.com
WindowsSystemRoot : C:\Windows
WindowsVersion : 1909
WindowsUBR : 752
```

Start by reproducing the failed push from an existing repository using the reported Git for Windows 2.26.1 and Keybase 5.3.0 versions, then compare it with cloning a repository and with the git-remote-keybase.exe symlink in C:\Program Files\Git\cmd\. Done means the keybase:// remote supports both the reported existing-repository workflow and the successful clone workflow, or the limitation is documented.

Written by the indexing model from the issue text.