#!/usr/bin/env bash

#

# Tries to cherry-pick merge commits from the main branch to the release branch.

# Adds comments to the original PRs of the problematic commits.

#

set -euo pipefail

MILESTONE="$1"

BRANCH="$2"

RELEASE_PATCH="$3"

check_not_empty \

MILESTONE \

BRANCH \

RELEASE_PATCH \

\

GITHUB_REPOSITORY \

DRY_RUN \

main_branch

SLACK_MESSAGE_FILE=$(mktemp)

# Increments PICKED variable if managed to pick a cherry.

cherry_pick() {

IFS=$'\t' read -r PR URL COMMIT _ AUTHOR TITLE <<<"$1"

# Skip commits merged before branching.

if git merge-base --is-ancestor "$COMMIT" HEAD; then

gh_log debug "$COMMIT is already on the release branch"

return

fi

# Find commits with the specific commit message after the fork point

# to not cherry-pick twice the same commit.

ALREADY_PICKED_CHERRIES=$(git log \

--grep "^(cherry picked from commit $COMMIT)\$" --format='%H' \

HEAD..."$FORK_POINT")

if [ -n "$ALREADY_PICKED_CHERRIES" ]; then

gh_summary "Already picked cherries for commit $COMMIT:\n\`\`\`\n$ALREADY_PICKED_CHERRIES\n\`\`\`"

return

fi

if git cherry-pick -x "$COMMIT"; then

gh_summary "Cherry-picked $COMMIT from PR $PR"

[ "$DRY_RUN" = "false" ] &&

gh pr comment "$PR" --body "Merge commit has been cherry-picked to branch \`$BRANCH\`."

PICKED=$((PICKED+1))

else

git cherry-pick --abort

[ "$DRY_RUN" = "false" ] &&

gh pr comment "$PR" --body "Please merge the changes to branch \`$BRANCH\`."

gh_summary "* [PR $PR]($URL) by **${AUTHOR}** (_${TITLE}_) could not be cherry-picked. Merge commit: \`$COMMIT\`."

echo "- <$URL|PR $PR> by *$AUTHOR* — $TITLE" \

>>"$SLACK_MESSAGE_FILE"

fi

}

find_fork_point() {

set +o pipefail

diff -u \

<(git rev-list --first-parent "$1") \

<(git rev-list --first-parent "$2") |

sed -ne 's/^ //p' |

head -1

set -o pipefail

}

# shellcheck disable=SC2154

PR_COMMITS=$(gh pr list -s merged \

--search "milestone:$MILESTONE" \

--base "$main_branch" \

--json mergedAt,number,url,mergeCommit,author,title \

--jq 'sort_by(.mergedAt) | .[] | "\(.number)\t\(.url)\t\(.mergeCommit.oid)\t\(.mergedAt)\t\(.author.login)\t\(.title)"')

if [ -n "$PR_COMMITS" ]; then

echo "Commits of merged PRs:"

echo "$PR_COMMITS"

echo "..."

fi

FORK_POINT=$(find_fork_point "$BRANCH" "$main_branch")

gh_log debug "Fork point: $FORK_POINT"

if [ -n "$PR_COMMITS" ]; then

PICKED=0

while read -r PR_COMMIT; do

cherry_pick "$PR_COMMIT"

done <<<"$PR_COMMITS"

fi

# Replace % with %25, escape \n and " to pass as step output to Slack message.

FAILED=$(sed ':a; N; $!ba; s/%/%25/g; s/\n/\\n/g; s/"/\\"/g' "$SLACK_MESSAGE_FILE")

rm -f "$SLACK_MESSAGE_FILE"

if [ -n "$FAILED" ]; then

gh_output bad-cherries "$FAILED"

gh_summary <<EOF

As some of the PRs could not be cherry-picked, please help the authors to merge

their changes to the release branch via opening PRs.

The commands may look like the following (mind the placeholders):

# In the directory of the $GITHUB_REPOSITORY clone:

git switch "$main_branch"

git pull

git switch --create <AUTHOR>/merge-pr-<PR NUMBER>-"$RELEASE_PATCH" \\

"$BRANCH"

git cherry-pick -x <MERGE COMMIT SHA>

# Proceed to resolve merge conflicts. Once done:

git push --set-upstream origin \$(git branch --show-current)

# Create PR to the release branch (assuming 'gh' is installed):

gh create pr --base "$BRANCH" --fill \\

--milestone "$MILESTONE"

EOF

exit 1

fi