The changes for #100 broke the way that buildifier reports errors, because we assume that the filename is called "stdin", and after #101, it's the value of -path:

https://github.com/google/vim-codefmt/blob/4b6cb67/autoload/codefmt/buildifier.vim#L57

This results in e.g.

Error formatting file: ERROR(ShellError): Error running: buildifier -path /home/malcolmr/foo/bar/BUILD
/home/malcolmr/foo/bar/BUILD:112:13: syntax error near cc_library