Look up when two branches get in trouble

git-when-conflict

#!/usr/bin/env bash
#
# Usage: git when-conflict master
#
# - Be on a clean branch (double check via `git status`).
# - Test that branch against another one (e.g. "master").
#
# Cheers!
#

currentHash=$(git rev-parse --abbrev-ref HEAD)
baseHash=$(git merge-base $1 $currentHash)

echo "From $baseHash to $currentHash:"

function testMerge() {
	git merge --abort &> /dev/null
	for testHash in $(git log --reverse --pretty=format:"%H" $baseHash..$1); do
		echo -n $testHash ...
		git merge --no-commit --no-ff $testHash &> /dev/null
		mergeStatus=$?

		if [[ $mergeStatus -ne 0 ]]; then
			echo "FAILED!"
			git log -n1 --pretty=format:"	%h %ci %cn (%ce) %s"
			echo ""
			echo "	Files with conflict:"
			git diff --name-only --diff-filter=U | sed 's/^/	/'
			git merge --abort &> /dev/null
			
			return
		fi

		echo " clean!"
	done
}

echo "Merging $currentHash into $1 ..."
testMerge $1

git checkout origin/$1 &> /dev/null

echo "Merging $1 into $currentHash ..."
testMerge $currentHash

git checkout $currentHash &> /dev/null

if [[ "$(git rev-parse --abbrev-ref HEAD)" != "$currentHash" ]]; then
	echo "Could not return to normal live."
	echo "Please checkout "$currentHash" before continuing!"
fi