[docker] Add workdir attribute

The workdir attribute set the initial working directory
when starting the docker container.

Contrary to the WORKDIR directive (see
https://docs.docker.com/reference/builder/#workdir), it only affects
the entry point.

--
MOS_MIGRATED_REVID=104201472

1 files changed, 12 insertions, 1 deletions

diff --git a/tools/build_defs/docker/README.md b/tools/build_defs/docker/README.md
index 3d93ec45ce..a225f5c259 100644
--- a/tools/build_defs/docker/README.md
+++ b/tools/build_defs/docker/README.md
@@ -181,7 +181,7 @@ docker_build(
 ### `docker_build`
 
 `docker_build(name, base, data_path, directory, files, mode, tars,
-debs, symlinks, entrypoint, cmd, env, ports, volumes)`
+debs, symlinks, entrypoint, cmd, env, ports, volumes, workdir)`
 
 <table>
   <thead>
@@ -322,6 +322,17 @@ debs, symlinks, entrypoint, cmd, env, ports, volumes)`
                of volumes to mount.</a></p>
       </td>
     </tr>
+    <tr>
+      <td><code>workdir</code></td>
+      <td>
+        <code>String, optional</code>
+        <p><a href="https://docs.docker.com/reference/builder/#workdir">Initial
+               working directory when running the docker image.</a></p>
+        <p>Because building the image never happen inside a docker container,
+               this working directory does not affect the other actions (e.g.,
+               adding files).</p>
+      </td>
+    </tr>
   </tbody>
   </tbody>
 </table>