GODRIVER-2978 Automate syncing code between Go driver v1 and v2

docs/CONTRIBUTING.md

@@ -29,6 +29,18 @@ If any tests do not pass, or relevant tests are not included, the patch will not
 
 If you are working on a bug or feature listed in Jira, please include the ticket number prefixed with GODRIVER in the commit message and GitHub pull request title, (e.g. GODRIVER-123). For the patch commit message itself, please follow the [How to Write a Git Commit Message](https://chris.beams.io/posts/git-commit/) guide.
 
+### Cherry-picking between branches
+
+If a Pull Request needs to be cherry-picked to a new branch, get the sha of the commit in the base branch, and then run
+
+```bash
+bash etc/cherry-picker.sh <sha>
+```
+
+The cherry-picker script is configured to use `v1` as the base branch and `master` as the target branch.
+It will create a new checkout in a temp dir, create a new branch, perform the cherry-pick, and then
+prompt before creating a PR to the target branch.
+
 ## Testing / Development
 
 The driver tests can be run against several database configurations. The most simple configuration is a standalone mongod with no auth, no ssl, and no compression. To run these basic driver tests, make sure a standalone MongoDB server instance is running at localhost:27017. To run the tests, you can run `make` (on Windows, run `nmake`). This will run coverage, run go-lint, run go-vet, and build the examples.

etc/cherry-picker.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+
+sha=$1
+base=v1
+target=master
+dirname="/tmp/go-driver-$(openssl rand -hex 12)"
+mkdir -p $dirname
+git clone git@github.com:mongodb/mongo-go-driver.git $dirname
+cd $dirname
+branch="cherry-pick-$sha"
+git fetch origin $base
+git fetch origin $target
+git checkout -b $branch origin/$target
+git cherry-pick -x $sha
+
+old_title=$(git --no-pager log -1 --pretty=%B | head -n 1)
+ticket=$(echo $old_title | sed -r 's/([A-Z]+-[0-9]+).*/\1/')
+echo "ticket $ticket"
+text=$(echo $old_title | sed -r 's/([A-Z]+-[0-9]+) (.*) \(#[0-9]*\)/\2/')
+echo "text $text"
+pr_number=$(echo $old_title| sed -r 's/.*(#[0-9]*)\)/\1/')
+echo "pr number: $pr_number"
+title="$ticket [$target] $text"
+body="Cherry-pick of $pr_number from $base to $target"
+
+echo
+echo "Creating PR..."
+echo "Title: $title"
+echo "Body: $body"
+echo
+
+read -p 'Push changes? (Y/n) ' choice
+if [[ "$choice" == "Y" || "$choice" == "y" || -z "$choice" ]]; then
+ gh pr create --title "$title" --base $target --body "$body"
+fi