title: postinstall autorebase not running cleanly
body: <p>I am always getting an error when I add a package to cygwin, for example:
  Package: Unknown package
      autorebase.bat exit code 1</p>
  
  <p>/var/log/setup.log.full indicates the problem:</p>
  
  <pre><code>2013/12/02 10:07:57 running: cmd.exe /c "C:\cygwin64\etc\postinstall\autorebase.bat"
  2013/12/02 10:07:57 abnormal exit: exit code=1
  </code></pre>
  
  <p>Running cmd.exe /c "C:\cygwin\etc\postinstall\autorebase.bat" complains about dash not being found.</p>
  
  <pre><code>C:\Users\xxx&gt;cmd /c C:\cygwin64\etc\postinstall\autorebase.bat
  'dash' is not recognized as an internal or external command,
  operable program or batch file.
  </code></pre>
  
  <p>So I changed autorebase.bat  from</p>
  
  <pre><code>@echo off
  rem Postinstall scripts are always started from the Cygwin root dir
  rem so we can just call dash from here
  path .\bin;%path%
  dash /bin/rebaseall -p
  </code></pre>
  
  <p>to</p>
  
  <pre><code>@echo off
  rem Postinstall scripts are always started from the Cygwin root dir
  rem so we can just call dash from here
  C:
  cd C:\cygwin64
  path .\bin;%path%
  dash /bin/rebaseall -pv
  </code></pre>
  
  <p>After this change I can run cmd /c C:\cygwin64\etc\postinstall\autorebase.bat cleanly from the command prompt but the error still shows up when I add a package using a installer.</p>
  
  <p>How do I fix this?</p>