Fixed an error updating shallow submodules

[EduardTalanov]

When we try to execute
submodule_update(recursive=True, init=True)
in Repo class with shallow submodules, command
git fetch --progress -v origin
sometimes print log such as
=5 = [up to date] zm/160_uwp -> origin/zm/160_uwp
but it doesn't satisfy filter:
r"^ (.) ([[\w .$@]+]|[\w.$@]+) +(.+) -> ([^ ]+)( (.)?$)?"
and throw exception.
I've updated it so that it works correctly.

[Byron]

Do these numbers in =5 = [up to date] zm/160_uwp -> origin/zm/160_uwp (=5 =) look like an issue with parallelism on the server side, or do they have meaning?

[EduardTalanov]

I don't think so. I've found this number only in one branch. Other branches didn't have this number.

[Byron]

Thank you.

The new regex would unconditionally consume up to three characters, just as long as there is one more to capture, followed by a space.

This should be safe and handle this particular case.