Is there some debug variable I need to turn on?
magit-git-debug is a variable defined in ‘magit-git.el’.
Its value is nil
Whether to enable additional reporting of git errors.
Magit basically calls git for one of these two reasons: for
side-effects or to do something with its standard output.
When git is run for side-effects then its output, including error
messages, go into the process buffer which is shown when using M-x magit-process.
When git’s output is consumed in some way, then it would be too
expensive to also insert it into this buffer, but when this
option is non-nil and git returns with a non-zero exit status,
then at least its standard error is inserted into this buffer.
This is only intended for debugging purposes. Do not enable this
permanently, that would negatively affect performance.