Whereas before niv would simply say that git didn't produce any output,
it now points out that the branch may not exist:
*Niv> :main add git git@github.com:nmattia/niv -b foobar
Adding package niv
FATAL: Could not read the output of 'git'.
command: git ls-remote git@github.com:nmattia/niv refs/heads/foobar
Git didn't produce any output. Does the branch 'foobar' exist?
FATAL: One or more packages failed to update:
niv: ExitFailure 1
ERROR: ExitFailure 1
*** Exception: ExitFailure 1
Whereas before niv would simply say that git didn't produce any output, it now points out that the branch may not exist:
Closes #176