This is a reland of 72a245e4

The "git checkout master --detach" operation has been modified to run in the solution
directory.

Original change's description:
> Fetch the input commit ref when both ref and id are specified.
>
> This causes --refs refs/head/master to be added to bot_update calls when
> the input build message contains a commit id and the refs/head/master
> ref. This is an effective no-op.
>
> When bot_update clones a git repository, it results in HEAD referring to
> master in contrast to the non-clone case which results in a detached
> HEAD. This prevents fetching refs/heads/master, so detach the HEAD after
> cloning.
>
> Bug: 922150
> Change-Id: I357a78305020218e9f5d350832a706b8f2b27967
> Recipe-Nontrivial-Roll: build
> Recipe-Nontrivial-Roll: build_limited_scripts_slave
> Recipe-Nontrivial-Roll: infra
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1900735
> Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
> Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>

Bug: 922150
Change-Id: I7dc6ebed2dcbd880ff4d515f7e9fc6428ff24099
Recipe-Nontrivial-Roll: build
Recipe-Nontrivial-Roll: build_limited_scripts_slave
Recipe-Nontrivial-Roll: infra
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1910260Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>