At work, I use a mix of Git for Windows, Atlassian’s Sourcetree, and Magit in Emacs. The latter is what I am trying to use fulltime, but old habits tend to stick around.
For some reason, however, I would get the following error message when trying to pull/push/fetch from the origin remote:
128 git.exe … "fetch" "origin"
fatal: protocol error: bad line length character: git@
When faced with this error, I always reverted to using Sourcetree, as that has been my previous main Git client. When this had happened one to many times, I had the clarity to check the raw Git log in Magit. There, I think I was able to see that the error message was preceeded by an authentication issue. As I use Plink from the PuTTY project to load my certificate, I was struck with the obvious answer, that I hadn’t loaded my certificate which I use for authentication. After I ensured that Plink was started with the correct certificate loaded, Magit started working immediately!