Add --all flag to fetch method

The fix for CVE-2022-25648 broke a workflow for us by removing the ability
to fetch all remotes.

This adds --all to the list of available flags for the #fetch method. It does
not add `:a` as an alternative flag, as `git fetch -a` and `git fetch --all` are
not the same thing.

Signed-off-by: Matthew Riedel <matthew.riedel@fluxfederation.com>

lib/git/lib.rb

@@ -877,6 +877,7 @@ def tag(name, *opts)
 
     def fetch(remote, opts)
       arr_opts = []
+      arr_opts << '--all' if opts[:all]
       arr_opts << '--tags' if opts[:t] || opts[:tags]
       arr_opts << '--prune' if opts[:p] || opts[:prune]
       arr_opts << '--prune-tags' if opts[:P] || opts[:'prune-tags']