As of today (Aug 26) git-drover is not available, if you do a man drover-git, you will get the following message:
GIT-DROVER(1) Chromium depot_tools Manual GIT-DROVER(1)
git drover is NOT IMPLEMENTED yet. See the EXAMPLE section for the equivalent sequence of commands to run.
So the following instructions are designed to achieve merge functionality manually via git.
Pre-Req: Setup your Chromium checkout
fetch --nohooks chromium
git checkout master
Step 1: Creating a branch
gclient sync --with_branch_heads
git checkout -b drover_<branch number> branch-heads/<branch number>
Step 2: Merge/Revert
To Drover Merge
git cherry-pick -x <git hash of the change you want to merge>
To Drover Revert
git revert <git hash of the change you want to merge>
Step 3: Submit your change
git cl upload
git cl land --bypass-hooks
Step 4: Next time you need to merge something
Merging to a branch and don't know the branch number? The TPM (release manager) approving the merge will have it.