Pushing everything

I'd like to push all my branches and tags to the server, but for whatever reason 
"--all" ignores tags and is incompatible with "--tags". I could imagine there's 
a reason I'm not experienced enough to see?

It seems to me that "--mirror" is quite unusable, since it force-overwrites the 
remote repo and even deletes refs not locally present. Obviously, a mirror can't 
be shared, and it doesn't seem to me to be the ideal backup solution for a 
single person.

However, even if "git push -all -tags"  worked, I'm not sure it's a good idea 
for project with more collaborators. There may be conflicts or other problems 
and quite often the pushing occurs just before leaving so it's no good time to 
start resolving conflicts. Can a shared repo be used as a sort of backup as 
well? I'd like a possibility to backup all my work there anytime without needing 
to care about anything. This could work by creating sort of private refs in case 
of any problems, or whatever. Is there something like this, or am I thinking 
astray? I'd suppose, something like this could be very useful for a company 
where it'd provide a simple backup solution for everybody.