Find local git branches with a closed GitHub PR

merged-branches.sh

#!/bin/bash

# Outputs commands to delete local branches that have an
# associated merged (really closed) PR.
# In particular, this also works if the remote branch was
# before merging rebased remotely.

# BIG CAVEAT: This will report branches that have a closed,
# but not merged PR for deletion.

# Assumes two environment vars to exist:
# GITHUB_USERNAME
# GITHUB_TOKEN

for branch in $(git for-each-ref --format='%(refname)' refs/heads/); do
  # Find closed PRs associated with the branch name.
  # Note, that this ignores whether the PR was merged.
  # TODO: Filter for only merged PRs.
  json=$(curl --silent -X GET -H "User-Agent: amp-changelog-gulp-task" \
    -u $GITHUB_USERNAME:$GITHUB_TOKEN \
    -H "Accept: application/vnd.github.v3+json" -H "Content-Type: application/json" \
    -H "Cache-Control: no-cache" \
    "https://api.github.com/repos/ampproject/amphtml/pulls?state=closed&head=$GITHUB_USERNAME:$branch" 2>&1)
  if [[ $json == {* ]];then
    echo "ERROR $json"
    exit 1
  fi
  if [ "$json" != "[]" ];then
    echo "git update-ref -d $branch"
  fi
done