bash-only features, and /bin/sh is not a symlink to bash on all systems.
* If an input file is a Windows absolute path (e.g. "C:\foo\bar.proto") and
  the import path only contains "." (or contains "." but does not contain
  the file), protoc incorrectly thought that the file was under ".", because
  it thought that the path was relative (since it didn't start with a slash).
  This has been fixed.