mv.rb

require 'fileutils'
require 'tmpdir'

# FileUtils.mv
#
# Ruby 1.8.7's FileUtils.mv calls File.rename on the src. However, File.rename
# raises Errno::EXDEV when src and dst exist on separate devices. The fallback
# is to perform a copy instead of a rename.
#
# However, there is a bug in 1.8.7's implementation. If src is a symlink or a
# directory containing a symlink, and the target of that symlink has not yet been
# copied, the copy will fail, because copy_metadata calls File.utime on the
# symlink. File.utime resolves symlinks, and because the target does yet exist,
# it raises Errno::ENOENT.
#
# This was fixed in Ruby here:
# https://github.com/ruby/ruby/commit/7d89ecdc523aab7b9908501b6743da2c26a53825

# ***NOTE***: This is an entirely different problem than the one that prompted
# the introduction of HOMEBREW_TEMP. In that case, the BSD mv(1) command bails
# out if we're moving a symlink across volumes when the target has *already*
# been moved. We only see this when Pathname#install_p is fed a symlink directly,
# as that is the only case in which we exec mv(1) rather than using FileUtils.mv.

if RUBY_VERSION.to_f < 1.9
  class FileUtils::Entry_
    def copy_metadata(path)
      st = lstat()
      if !st.symlink?
        File.utime st.atime, st.mtime, path
      end
      begin
        if st.symlink?
          begin
            File.lchown st.uid, st.gid, path
          rescue NotImplementedError
          end
        else
          File.chown st.uid, st.gid, path
        end
      rescue Errno::EPERM
        # clear setuid/setgid
        if st.symlink?
          begin
            File.lchmod st.mode & 01777, path
          rescue NotImplementedError
          end
        else
          File.chmod st.mode & 01777, path
        end
      else
        if st.symlink?
          begin
            File.lchmod st.mode, path
          rescue NotImplementedError
          end
        else
          File.chmod st.mode, path
        end
      end
    end
  end
end

begin
  Kernel.system "diskutil erasevolume HFS+ 'fileutilstmp' $(hdiutil attach -nomount ram://1024)"

  Dir.mktmpdir do |dir|
    Dir.chdir dir do
      FileUtils.mkdir 'foo'
      FileUtils.mkdir 'bar'
      FileUtils.ln_s '../bar', 'foo/bar'

      begin
        FileUtils.mv 'foo', '/Volumes/fileutilstmp'
      rescue Errno::ENOENT
        puts "Ruby 1.8.7's FileUtils.mv blows."
      end
    end
  end
ensure
  Kernel.system "umount", "/Volumes/fileutilstmp"
end