Merginator: Merge master/release branches back into development

merginator.sh

#!/bin/bash -ex
# -ex = e: fail if any non zero, x: print commands prior to running

# This script ensures that the development branch and all release branches are up to date with the branches that preceed it. master is first, then release-X in order by name, followed by development.

# How it works:
#
# 1. Strip the current branch to its raw form. (origin/master -> master, origin/release-2.5.3 -> release-2.5.3)
# 2. If the current branch is master, set the START_MERGING variable to true.
# 3. Get all the current release branches, ordered by name ascending (so 2.5.3 comes before 2.5.4 and 2.5.5)
# 4. Loop over each release branch.
#     a. Keep going through the branches until you find the current branch. Once you've found it, set the START_MERGING to true
#     b. If START_MERGING is set:
#         - Checkout that release branch
#         - Pull it
#         - Merge in the current branch
#         - Push it
#         - Exit.
# 5. If you never exited (i.e. never found another branch) then merge the branch into development and push that.


echo_green() {
    echo -e "\E[32;47m$1\E[30;47m" # Echo in green, then reset to black
}

merge_branch() {
    echo_green "Checking out $1 and merging $2 into it"

    git checkout $1
    git pull
    git merge $2
    git push
}

GIT_BRANCH=`echo $1`
CURRENT_BRANCH=`echo $1 | cut -d'/' -f2-` # Strip off the origin/ from the branch.

START_MERGING=false

git remote update origin --prune # Update the remote branch list

# If we're on the master branch, we'll merge back through all the release branches.
if [[ $CURRENT_BRANCH == 'master' ]]
then
    echo_green "On master branch, so merging this and all release branches backwards"
    START_MERGING=true
fi

# Loop through each of the current release branches (ordered by name, because 2.5.4 is after 2.5.3 when ordered by name)
while read -r releaseBranch
do
    echo_green "Checking Release Branch: $releaseBranch"

    if [[ $releaseBranch = $CURRENT_BRANCH ]]
    then
        START_MERGING=true
        continue # Don't merge this branch. That'd be silly.
    fi

    if [[ $START_MERGING = true ]]
    then
        merge_branch $releaseBranch $GIT_BRANCH
        exit 0 # Exit. The reason for this is we've just pushed to a branch that is also monitored by Jenkins. That will trigger this script and handle the next branch in the pile.
    fi
done < <(git for-each-ref --sort=refname refs/remotes/origin --format='%(refname)' | grep "release-" | cut -d'/' -f4-)

# Only merge into development if we haven't merged any others. I.e. this is the last one.
merge_branch development $GIT_BRANCH