gpr

#!/usr/bin/env bash

function help() {
  pr=123
  local_ref=foo
  script="$(basename "$0") $pr"
  cat <<HELP
-=[ GitHub Pull Request Helper]=-

  Usage: $(basename "$0") pull_request_id [ step ]

-=[ Description ]============================================================-

  The "step" argument can be used to force execution of a particular step,
  but by default this script will automatically choose the next step, from
  STEP 1 to STEP 2 and finally to STEP 3. You'll have to execute STEP 4
  manually, once everything is done.

-=[ Detailed workflow example ]==============================================-

  For this example, assume PR $pr has been filed against the "$local_ref" branch.

  -=[ STEP 1 ]=-

  You run "$script" and this executes:

$(help_step1)

  -=[ STEP 2 ]=-

  You run "$script" and this executes:

$(help_step2)

  -=[ STEP 3 ]=-

  You run "$script" and this executes:

$(help_step3)

  -=[ STEP 4 ]=-

  You run "$script 4" (explicitly specifying the 4) and this executes:

$(help_step4)

-=[ Very important notes ]===================================================-

  Before running this script, ensure that your local "$local_ref" branch is
  up-to-date!

  At the beginning of STEP 1, any existing "pr$pr" and "pr$pr-squash"
  branches will be deleted.

  At the beginning of STEP 2, any existing pr$pr-squash" branch will be
  deleted.

  If you want to hide per-step explanations, set ENV var GPR_SHH=1. For
  example, create an alias like: alias gpr='GPR_SHH=1 gpr'

-=[ License ]================================================================-

  
  Licensed under the MIT license.
  
HELP
  [[ "$1" ]]; exit
}

function help_step1() {
  echo "  Fetch and rebase PR $pr into \"pr$pr\" branch"
  [[ "$1" ]] && return
  cat <<HELP
   1. Fetch the repo and branch associated with PR $pr.
   2. Checkout a new "pr$pr" branch at the HEAD of the fetched branch.
   3. Rebase "$local_ref" branch onto "pr$pr" branch.
   4. Display a list of files changed in the PR.

  Note that you may need to resolve conflicts. If the rebase is successful,
  test the PR and commit fixes. Commit as many times as necessary; It doesn't
  matter because all PR-related commits will be squash merged in STEP 2.
HELP
}

function help_step2() {
  echo "  Perform squash merge into \"pr$pr-squash\" branch"
  [[ "$1" ]] && return
  cat <<HELP
   1. Checkout a new "pr$pr-squash" branch from "$local_ref" branch.
   2. Squash merge "pr$pr" branch into "pr$pr-squash" branch. (no commit)
   3. Append "Closes gh-$pr." to SQUASH_MSG.
   4. Commit using the PR branch's HEAD author name.

  Since all the commits in the PR have been squashed into one commit, you will
  need to edit the commit message. When done, inspect the commit log, ensuring
  everything is perfect; you should see a single, beautiful commit.
HELP
}

function help_step3() {
  echo "  Perform final merge into \"$local_ref\" branch"
  [[ "$1" ]] && return
  cat <<HELP
   1. Checkout "$local_ref" branch.
   2. Merge "$pr-squash" branch into "$local_ref" branch.

  If STEP 2 was successful, there should be no conflicts here. If there are,
  you're doing it wrong. Just double-check the commit log and push when done.
HELP
}

function help_step4() {
  echo "  Cleanup temporary branches and tags"
  [[ "$1" ]] && return
  cat <<HELP
   1. Temporary "pr$pr" and "pr$pr-squash" branches are deleted.
   2. Temporary "_pr${pr}_author_head" tag is deleted.
HELP
}

function header() {
  if [[ "$GPR_SHH" ]]; then
    echo "-=[ STEP $1 ]=================================================================-"
  else
    echo "-=[ STEP $1 Overview ]========================================================-"
    help_step$1
    echo
    echo "-=[ Actual ]=================================================================-"
  fi
}

[[ ! "$1" || "$1" == "-h" || "$1" == "--help" ]] && help $1

# Generate and store an OAUTH token.
if [[ "$1" == "auth" ]]; then
  read -p 'Enter GitHub username: '
  json="$(curl -fsSL --data '{"note":"gpr","scopes":["repo"]}' https://api.github.com/authorizations -u "$REPLY")"
  if [[ "$json" ]]; then
    token="$(node -pe "($json).token")"
    git config --global --remove-section gpr 2>/dev/null
    git config --global --add gpr.token $token
    echo "Authorization successful, token saved."
    exit
  else
    echo "Error authorizing with GitHub, please try again."
    exit 5
  fi
fi

pr="$1"; shift
script="$(basename "$0") $pr"
branch="pr$pr"

repo="$(git remote show -n origin | perl -ne '/Fetch URL: .*github\.com[:\/](.*\/.*)\.git/ && print $1')"

# Let's fetch some JSON.
token="$(git config --get gpr.token)"
json="$(curl -fsSL "https://api.github.com/repos/$repo/pulls/$pr?access_token=$token" 2>/dev/null)"
if [[ $? != 0 || ! "$json" ]]; then
  echo "Error fetching GitHub API data for $repo PR $pr!"
  echo "If you're trying to access a private repo and haven't yet done so, please run"
  echo "the \"$(basename "$0") auth\" command to generate a GitHub auth token."
  exit 2
fi

# Let's parse some JSON.
remote_url="$(node -pe "($json).head.repo.git_url")"
remote_ref="$(node -pe "($json).head.ref")"
local_url="$(node -pe "($json).base.repo.git_url")"
local_ref="$(node -pe "($json).base.ref")"
num_commits="$(node -pe "($json).commits")"

# Let's get the project's .git folder.
git_dir="$(git rev-parse --show-toplevel)/.git"

function del_branch() {
  if [[ "$(git branch | grep " $1\$")" ]]; then
    git checkout "$local_ref" 2>/dev/null
    git branch -D "$1" 2>/dev/null
  fi
}

# Use the specified step, otherwise attempt to auto-detect it.
if [[ "$1" ]]; then
  step=$1
elif [[ "$(git branch | grep " $branch-squash\$")" ]]; then
  # STEP 3 should never auto-execute twice.
  if [[ "$(git branch --contains "$(git rev-parse $branch-squash)" | grep " $local_ref\$")" ]]; then
    echo "Error merging branch \"$branch-squash\" into \"$local_ref\" branch! (already done)"
    echo
    echo "Redo the last step with: $script 3"
    exit 4
  fi
  step=3
elif [[ "$(git branch | grep " $branch\$")" ]]; then
  step=2
else
  step=1
fi

# Let's do some stuff.
if [[ $step == 1 ]]; then
  header 1

  # Clean up any prior work on this PR.
  del_branch "$branch"
  del_branch "$branch-squash"

  # Fetch remote, create a branch, etc.
  if [[ "$remote_url" == "$local_url" ]]; then
    git fetch origin "$remote_ref"
  else
    git fetch "$remote_url" "$remote_ref"
  fi
  git checkout -b "$branch" FETCH_HEAD

  # Save ref to last PR author commit for later use
  git tag --force "_${branch}_author_head" FETCH_HEAD

  # Rebase!
  git rebase "$local_ref"
  if [[ $? != 0 ]]; then
    echo "Error while attempting rebase!"
    exit 3
  fi

  echo
  echo "Changed files in HEAD~$num_commits:"
  git --no-pager diff --name-only HEAD~"$num_commits"

  echo
  echo "-=[ Next Steps ]=============================================================-"
  echo "$(help_step2 1) with: $script"
  echo "  Or redo the current step with: $script 1"

elif [[ $step == 2 ]]; then
  header 2

  # Clean up any prior squashes for this PR.
  del_branch "$branch-squash"

  # Create branch and squash merge all commits.
  git checkout -b "$branch-squash" "$local_ref"
  git merge --squash "$branch"

  # Append useful information to commit message.
  squash_msg_file="$git_dir/SQUASH_MSG"
  echo -e "\nCloses gh-$pr." >> "$squash_msg_file"

  # Retrieve author name and email from stored commit, and commit.
  author="$(git log "_${branch}_author_head" -n1 --format="%an <%ae>")"
  git commit --author="$author"

  echo
  echo "-=[ Next Steps ]=============================================================-"
  echo "$(help_step3 1) with: $script"
  echo "  Or redo the current step with: $script 2"

elif [[ $step == 3 ]]; then
  header 3

  # Actually merge squashed commits into branch.
  git checkout "$local_ref"
  git merge "$branch-squash"

  echo
  echo "-=[ Next Steps ]=============================================================-"
  echo "$(help_step4 1) with: $script 4"
  echo "  Or redo the current step with: $script 3"

elif [[ $step == 4 ]]; then
  header 4

  del_branch "$branch"
  del_branch "$branch-squash"
  git tag -d "_${branch}_author_head" 2>/dev/null

  echo
  echo "All done."
fi