commit eb2ae13ea9cb380a6ad173c725b14c98aafc083f
author Todd Wang <toddw@google.com> Thu Dec 03 12:11:36 2015 -0800
committer Todd Wang <toddw@google.com> Thu Dec 03 20:38:58 2015 +0000
tree 976e248fc14d77dac5ebce46d6794987bbce0125
parent 9f421c4adb07229f5af50c26ff72e4e98a511ddf

TBR jiri: Create and populate the .jiri_root dir

Our plans are to move to a new world order where there is a
.jiri_root directory that contains all the
root-level (i.e. non-project-level) jiri metadata.  This is a
step in that direction.

This CL creates the .jiri_root directory when "jiri update" is
run.  In our final state we want the bootstrap script to do this,
but we can't force everyone to re-run the bootstrap, so this is
part of the the transition logic.

We also populate this with two directories:
  root/.jiri_root/bin            # previously root/devtools/bin
  root/.jiri_root/update_history # previously root/.update_history

It's important to move the bin directory now, since we don't want
our shim script to change very often (or at all), so we need the
new location.  The "jiri update" logic now populates the new bin
directory, and we have transitional logic that backs up an
existing devtools/bin into .jiri_root/bin.BACKUP, and drops a
symlink from devtools/bin to .jiri_root/bin.

Also added the shim script, which is very straightforward.

MultiPart: 1/2
Change-Id: Ia90c337d2ec363d12033599fd2b3e303cd518a3a