Finds the release(s) for a given change.

Relies on using "git cherry-pick -x" per
http://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/git-drover.html
so that the merge commit message contains the original commit.

Example:

d:\src\cr3\src>git show -s 53cc88da9a258bc4a34c4bff50025ee044c2e64d
commit 53cc88da9a258bc4a34c4bff50025ee044c2e64d
Author: grt <grt@chromium.org>
Date:   Tue Jun 2 10:33:09 2015 -0700

    Beacons for tracking default browser status.

    BUG=488247
    R=gab@chromium.org,wfh@chromium.org

    Review URL: https://codereview.chromium.org/1146843003

    Cr-Commit-Position: refs/heads/master@{#332423}


"Now, where did that ship?"


d:\src\cr3\src>git find-releases 53cc88da9a258bc4a34c4bff50025ee044c2e64d
commit 53cc88da9a258bc4a34c4bff50025ee044c2e64d was:
  initially in 45.0.2421.0
  merged to 43.0.2357.126 (as 8a5ccc0e0ad6b2237b2fcfffcb0ab24fe97bc77b)
  merged to 44.0.2403.39 (as d5d165943a88e51a64fd9e2fbcc781e4aaee270f)

Review URL: https://codereview.chromium.org/1332473003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@296604 0039d316-1c4b-4281-b951-d872f2087c98