This reverts commit 568b7a89.

Reason for revert: temporary revert to revert previous CL.

Original change's description:
> Wipe out shallow checkout support from bot_update.
> 
> Bug: 855137
> Change-Id: I60b8d69f9ab353c12120d4216e3a12518f99732c
> Reviewed-on: https://chromium-review.googlesource.com/1111107
> Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
> Reviewed-by: Ryan Tseng <hinoka@chromium.org>

TBR=iannucci@chromium.org,hinoka@chromium.org,tandrii@chromium.org

Change-Id: Iede67717be448be9bdd7c5dd4895fbab9fd65c66
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 855137, 855700
Reviewed-on: https://chromium-review.googlesource.com/1111924Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>