Change merge conflict resolution instructions

[JoeRobich]

The steps for resolving merge conflicts locally for a merge PR read as follows.

git fetch --all
git checkout merges/master-to-master-vs-deps
git reset --hard upstream/master-vs-deps
git merge upstream/master
# Fix merge conflicts
git commit
git push upstream merges/master-to-master-vs-deps --force

Since the merge branch points to upstream/master, the step to reset the branch to upstream/master-vs-deps shows a big change in merges (obviously) and requires the use of a force push. I believe it would be simpler and provide a more expected experience to leave the branch pointing to upstream/master and to merge upstream/master-vs-deps into the merge branch.

These are the proposed instructions

git fetch upstream
git checkout merges/master-to-master-vs-deps
# Pull in latest changes
git reset --hard upstream/master 
git merge upstream/master-vs-deps
# Fix merge conflicts with `git mergetool` or by other means
git commit
git push upstream merges/master-to-master-vs-deps

[RikkiGibson]

I'm fine with this. I'd also consider changing the first line to git fetch upstream master master-vs-deps, and deleting and recreating the merges/* branch. But I'm particularly sensitive to the time needed to fetch everything, especially since I have 18 remotes in my local repo 😉