Add comment about fixing merge conflicts

When working with downstream branches chained to upstream branches, it
helps to use `git rebase -i @{u}` twice to pull upstream changes into
the downstream branch. Expect a lot of merge conflicts when you do
this, as git is often not smart enough to figure out which change
happened more recently, and should take precedence.

Bug: None
Change-Id: Ic742439981d6d63e8d6bd1e10776fa920c88eb7f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2341387
Reviewed-by: Michael Giuffrida <[email protected]>
Commit-Queue: Toby Huang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#796561}
1 file changed