git_float.sh

#!/bin/bash

set -e
set -u

# This script "floats" any number of local branches
# on top of a chosen base branch. So, when the base
# branch gets updated, it will move your whole tree
# of local branches on top of the new commits.
#
# Usage:
# git float [--merge] branch1 branch2 branch3
#
# It needs an environment variable set
# export GIT_FLOAT_BASE_BRANCH=<your branch name here>

CURRENT_BRANCH=$(git rev-parse --abbrev-ref HEAD)
INTEGRATION_BRANCH=local_integration

DO_MERGE=false
DO_PULL_UPSTREAM=true
if [ $# -ne 0 ]; then
    # Note: The way this is written, you can't supply both --merge and
    # --no-pull-upstream options. If that becomes necessary, then we might look
    # at rewriting this in Python.
    if [ "$1" = "--merge" ]; then
        DO_MERGE=true
        shift
    elif [ "$1" = "--no-pull-upstream" ]; then
        DO_PULL_UPSTREAM=false
        shift
    elif [[ "$1" == --* ]]; then
        echo "Unrecognized argument ${1}"
        exit 1
    fi
fi

# Alternate way; handling BRANCHES as a string instead of as an array.
# if [ $# -eq 0 ]; then
#     BRANCHES=$(git branch --format '%(refname:short)' --no-merged "$GIT_FLOAT_BASE_BRANCH")
# else
#     # http://stackoverflow.com/questions/3008695/what-is-the-difference-between-and-in-bash
#     BRANCHES="$*"
# fi

# Here's how to handle BRANCHES as an array instead of as a
# whitespace-delimited string. Use the array like this:
#    git merge --no-ff --no-edit "$BRANCHES"
declare -a BRANCHES
if [ $# -eq 0 ]; then
    # Make an array
    while IFS= read -r line; do
        # Trim whitespace
        # https://stackoverflow.com/questions/369758/how-to-trim-whitespace-from-a-bash-variable/369795#369795
        trimmed_line="${line//[[:space:]]/}"
        if ! [[
            ${trimmed_line} == 'alpha'
            || ${trimmed_line} == 'stage'
            || ${trimmed_line} == 'master'
            || ${trimmed_line} == 'dev'
            || ${trimmed_line} == 'develop'
        ]]; then
            echo "adding $trimmed_line"
            BRANCHES+=( "$trimmed_line" )
        fi
    done < <( git branch --format '%(refname:short)' --no-merged "$GIT_FLOAT_BASE_BRANCH" )

    # This doesn't work
    # https://stackoverflow.com/questions/11426529/reading-output-of-a-command-into-an-array-in-bash/32931403#32931403
    # read -r -a BRANCHES <<< "$(git branch --format '%(refname:short)' --no-merged "$GIT_FLOAT_BASE_BRANCH")"
else
    # Read the arguments as an array
    BRANCHES=("$@")
fi

if [ ${#BRANCHES[@]} -eq 0 ]; then
    echo "No branches to float"
    exit 0
else
    echo "Branches: ${BRANCHES[*]}"
fi

if [ "$CURRENT_BRANCH" == "$INTEGRATION_BRANCH" ]; then
    echo "You are on branch ${CURRENT_BRANCH}. Switch to a feature branch before running"
    exit 1
fi

echo "Float ${BRANCHES[*]} on top of $GIT_FLOAT_BASE_BRANCH"

git fetch --all --prune

git co "$GIT_FLOAT_BASE_BRANCH"

if [ "$DO_PULL_UPSTREAM" = "true" ]; then
    git up
fi

git branch -f "$INTEGRATION_BRANCH" "$GIT_FLOAT_BASE_BRANCH"

# Here we're iterating over a space-delimited string or a newline-delimited
# string Since IFS is at its default value of (space, tab, newline), this
# works. The alternative would be to make BRANCHES be an array variable.
for i in "${BRANCHES[@]}"
do
    git co "$i"
    git rebase --rebase-merges "$GIT_FLOAT_BASE_BRANCH"
done

git co "$INTEGRATION_BRANCH"

if [ "$DO_MERGE" = "true" ]; then
    for i in "${BRANCHES[@]}"
    do
        # Print out some octopi
        printf '🐙  '
    done
    printf '\n'

    git merge --no-ff --no-edit "${BRANCHES[@]}"
fi

git co "$CURRENT_BRANCH"