Change pull-local to just be a wrapper for pull with file:///

This follows up from the previous commit; now that pull knows how to
do the efficient link() or copy for local files, we can just have
pull-local call into ostree_repo_pull().

As part of this:
 - pull() can also accept a file:/// URI instead
   of a remote name (since pull local supports anonymous pulls)
 - pull() knows an "override-remote-name" option, since pull-local
   supported writing a ref out even if there wasn't a remote with
   that name

src/libostree/ostree-repo-private.h

@@ -162,6 +162,9 @@ _ostree_repo_commit_modifier_apply (OstreeRepo               *self,
                                     GFileInfo                *file_info,
                                     GFileInfo               **out_modified_info);
 
+gboolean
+_ostree_repo_remote_name_is_file (const char *remote_name);
+
 gboolean
 _ostree_repo_get_remote_option (OstreeRepo  *self,
                                 const char  *remote_name,