Starting with git 1.8.5, use the -C option.
git -C "/Users/michael/Development/Projects/opensource/dvsc-backup" status
Otherwise, you have to specify --work-tree as well as --git-dir
git --work-tree="/Users/michael/Development/Projects/opensource/dvsc-backup" --git-dir="/Users/michael/Development/Projects/opensource/dvsc-backup/.git" status