title: Get local hash of package
body: <p>Has anyone already implemented and exported a way to get the local SHA of an R package? <code>devtools</code> (via <code>local_sha()</code>) and <code>packrat</code> do this internally, but the functionality is not exported. There are situations that <a href="https://github.com/wlandau-lilly/drake/issues/6" rel="nofollow noreferrer">just require the hash</a>, plain and simple.</p>
  
  <p><strong>EDIT</strong>: From Gabor Csardi and Jim Hester:</p>
  
  <pre><code>install_github("hadley/devtools")
  packageDescription("devtools")$RemoteSha 
  ## [1] "a0c8d7333be185f979a60823dcfad66c9f3ea35e"
  packageDescription("devtools")$Version
  ## [1] "1.13.3.9000"
  </code></pre>
  
  <p>However, neither this solution nor <code>devtools:::local_sha()</code> accounts for packages installed from the source with <code>install.packages("package", type = "source", repos = NULL)</code>.</p>