GitLab Slackbot Script. Posts daily MRs to Slack to keep environments in sync. Blog here: https://medium.com/giant-machines/slackbot-to-the-rescue-keeping-gitlab-branches-in-sync-with-a-slackbot-ff84f80eaf5f

slackbot.sh

#!/usr/bin/env bash

# Function that will be called for each repo.  Script exectuion begins below.
handle_repo () {

  #1. Set up variables.
  local REPO=$1 # first function argument
  local PROJECT_ID=$2 # second function argument
  local SOURCE_BRANCH_DISPLAY=${3:-"QA"} # default value
  local TARGET_BRANCH_DISPLAY=${4:-"Dev"} # default value

  # Use exact (lowercase) branch name for Gitlab API calls
  local SOURCE_BRANCH=$(echo "$SOURCE_BRANCH_DISPLAY" | tr '[:upper:]' '[:lower:]' )
  local TARGET_BRANCH=$(echo "$TARGET_BRANCH_DISPLAY" | tr '[:upper:]' '[:lower:]' )

  local MR_TITLE="${SOURCE_BRANCH_DISPLAY} => ${TARGET_BRANCH_DISPLAY}"

  local SLACKBOT_BRANCH="slackbot%2fqa-to-dev" # URL escaped for API calls
  local SLACKBOT_BRANCH_DISPLAY="slackbot/qa-to-dev"

  if [ -z "$REPO" ] || [ -z "$SOURCE_BRANCH" ] || [ -z "$TARGET_BRANCH" ] || [ -z "$PROJECT_ID" ];  then
    echo "Missing environment variables: REPO: $REPO, SOURCE_BRANCH: $SOURCE_BRANCH, TARGET_BRANCH: $TARGET_BRANCH, PROJECT_ID: $PROJECT_ID"
    return 1
  fi

  echo "Running handle_repo for $REPO: From $SOURCE_BRANCH to $TARGET_BRANCH for project $PROJECT_ID"

  #2. Delete existing slackbot branch
  DELETE_BRANCH_RESP=$(curl -X DELETE --header "PRIVATE-TOKEN: $GITLAB_TOKEN" "https://gitlab.com/api/v4/projects/$PROJECT_ID/repository/branches/$SLACKBOT_BRANCH")
  echo "delete branch resp is $DELETE_BRANCH_RESP"

  #3. Create remote slackbot branch off of source branch
  CREATE_BRANCH_RESP=$(curl -X POST --header "PRIVATE-TOKEN: $GITLAB_TOKEN" "https://gitlab.com/api/v4/projects/$PROJECT_ID/repository/branches?branch=$SLACKBOT_BRANCH&ref=$SOURCE_BRANCH")
  echo "create branch resp is $CREATE_BRANCH_RESP"

  #4. Create merge request to target branch
  CREATE_MR_RESP=$(curl -X POST --header "PRIVATE-TOKEN: $GITLAB_TOKEN" "https://gitlab.com/api/v4/projects/$PROJECT_ID/merge_requests?source_branch=$SLACKBOT_BRANCH&target_branch=$TARGET_BRANCH&simple=true" --data-urlencode "title=$MR_TITLE")
  echo "create MR resp is $CREATE_MR_RESP"

  # Handle Gitlab occasionally retaining yesterday's unmerged MR after delete/create
  ALREADY_EXISTS=$(echo "$CREATE_MR_RESP" | grep 'already exists')

  # 5. Get MR ID
  if [ -n "$ALREADY_EXISTS" ]; then
    MR_ID="${CREATE_MR_RESP//[^0-9]/}" # extract numbers from response string
    echo "MR already exists $MR_ID"
  else
    MR_ID=$(echo "$CREATE_MR_RESP" | python3 -c "import sys, json; print(json.load(sys.stdin)['iid'])")
  fi

  # 6. Get MR info from GitLab API
  sleep 10  # Wait for GitLab to calculate merge conflicts info
  MR_INFO_RESP=$(curl --header "PRIVATE-TOKEN: $GITLAB_TOKEN" "https://gitlab.com/api/v4/projects/$PROJECT_ID/merge_requests/$MR_ID")
  echo "MR info resp is $MR_INFO_RESP"

  # 7. Get MR URL
  URL=$(echo "$MR_INFO_RESP" | python3 -c "import sys, json; print(json.load(sys.stdin)['web_url'])")

  # 8. Set initial slack message
  MSG="$REPO: $MR_TITLE: $URL"
  echo "New MR: $MSG"

  # 9. Report on merge conflicts
  CONFLICTS=$(echo "$MR_INFO_RESP" | python3 -c "import sys, json; print(json.load(sys.stdin)['has_conflicts'])")

  if [ "$CONFLICTS" == 'True' ]; then
    MSG="$MSG. *Merge Conflicts!* 🙀 _Pull down $SLACKBOT_BRANCH_DISPLAY, merge ${TARGET_BRANCH} into it locally, resolve conflicts, then push back up._ 😸"
  fi

  # 10. If MR is empty, close it
  CHANGES=$(echo "$MR_INFO_RESP" | python3 -c "import sys, json; print(json.load(sys.stdin)['changes_count'])")
  echo "changes count is $CHANGES"

  if [ "$CHANGES" == "None" ]; then
    echo "No changes, closing MR"
    MSG="$REPO: $SOURCE_BRANCH_DISPLAY is synced with $TARGET_BRANCH_DISPLAY! 🎉"
    curl -X PUT --header "PRIVATE-TOKEN: $GITLAB_TOKEN" "https://gitlab.com/api/v4/projects/$PROJECT_ID/merge_requests/$MR_ID?state_event=close"
  fi

  # 11. Send to Slack
  curl -X POST -H 'Content-type: application/json' --data "{\"text\":\"$MSG\"}" "$SLACK_URL"
}

# Begin script execution here:

# Setup env vars.  Located in the Gitlab project settings console.  For running locally, use a .env file at project root and export the vars.
if [ -f "./.env" ]; then
    source ./.env
    echo "Importing env vars from .env file"
fi

if [ -z "$SLACK_URL" ] || [ -z "$GITLAB_TOKEN" ] || [ -z "$REPO_DISPLAY_NAMES" ];  then
  echo "Missing environment Variables: SLACK_URL: $SLACK_URL, GITLAB_TOKEN: $GITLAB_TOKEN, REPO_DISPLAY_NAMES: $REPO_DISPLAY_NAMES"
  exit 1
fi

# Create array from comma-separated string of repo names
IFS=', ' read -r -a REPO_ARRAY <<< "$REPO_DISPLAY_NAMES"

# Call function for each repo.  For each repo name in the REPO_ARRAY, a matching variable with the GitLab project ID named with the repo name in all caps followed by _ID is required
for REPO in "${REPO_ARRAY[@]}"; do
  REPO_ID="$(echo "$REPO" | tr '[:lower:]' '[:upper:]')_ID" # Capitalize repo display name and add "_ID" to get project id's variable name

  handle_repo "$REPO" "${!REPO_ID}" # Indirect variable. REPO_ID's value is another variable's name, such as FRONTEND_ID, and we access that second variable's value.
  # https://stackoverflow.com/questions/16553089/dynamic-variable-names-in-bash
done