prepare test to provide worktrees of different kinds as well (#301)

Author: Byron

git-discover/tests/fixtures/make_basic_repo.sh

@@ -12,4 +12,14 @@ git commit -q -am c2
 
 mkdir -p some/very/deeply/nested/subdir
 
-git init --bare bare.git
+git clone --bare --shared . bare.git
+
+git worktree add worktrees/a
+git worktree add worktrees/b-deleted
+
+rm -Rf worktrees/b-deleted
+
+cd bare.git
+git worktree add ../worktrees/from-bare/c
+git worktree add ../worktrees/from-bare/d-deleted
+rm -Rf -v ../worktrees/from-bare/d-deleted