git push --delete <url> <branch> fails if run outside a repository

When using `git push`, rather than specifying a remote by name, one can also specify a remote by URL, and this includes when the only operations being performed are to delete refs on the remote. This doesn't require any information about any local repository, but it fails unless the command is run from within an existing local Git repo.

This seems like a bug to me: there's no reason this shouldn't work. Clearly low priority, though, as this is a rare use case, and there's a simple workaround: just `cd` into any existing Git repo, or create a temporary empty repo to run the command from.

Simple test case attached; I've verified the behaviour the test script demonstrates on Git v2.36.1 on Cygwin, and on Git v2.34.1 (strictly, v2.34.1-1~bpo11) on Debian 11.

Cheers,

Adam