doc: "s/git apply/git am -3" in V8 guide

git apply does not preserve the original commit message. These updated
instructions offer a simpler flow for backporting.

PR-URL: nodejs#10665
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Gibson Fahnestock <[email protected]>
Reviewed-By: Michal Zasso <[email protected]>

Author: MylesBorins

doc/guides/maintaining-V8.md

@@ -177,8 +177,8 @@ https://crbug.com/v8/5199. From the bug we can see that it was merged by V8 into
 `v6.x` uses V8 5.1, the fix needed to cherry-picked. To cherry-pick, here's an
 example workflow:
 
-* Download and apply the commit linked-to in the issue (in this case a51f429). `curl -L https://github.com/v8/v8/commit/a51f429.patch | git apply --directory=deps/v8`. If the branches have diverged significantly, this may not apply cleanly. It may help to try to cherry-pick the merge to the oldest branch that was done upstream in V8. In this example, this would be the patch from the merge to 5.2. The hope is that this would be closer to the V8 5.1, and has a better chance of applying cleanly. If you're stuck, feel free to ping @ofrobots for help.
-* Modify the commit message to match the format we use for V8 backports. You may want to add extra description if necessary to indicate the impact of the fix on Node.js. In this case the original issue was descriptive enough. Example:
+* Download and apply the commit linked-to in the issue (in this case a51f429). `curl -L https://github.com/v8/v8/commit/a51f429.patch | git am -3 --directory=deps/v8`. If the branches have diverged significantly, this may not apply cleanly. It may help to try to cherry-pick the merge to the oldest branch that was done upstream in V8. In this example, this would be the patch from the merge to 5.2. The hope is that this would be closer to the V8 5.1, and has a better chance of applying cleanly. If you're stuck, feel free to ping @ofrobots for help.
+* Modify the commit message to match the format we use for V8 backports and replace yourself as the author. `git commit --amend --reset-author`. You may want to add extra description if necessary to indicate the impact of the fix on Node.js. In this case the original issue was descriptive enough. Example:
 ```
 deps: cherry-pick a51f429 from V8 upstream