git-conflicted-branches.sh

#!/bin/bash

set -e

git fetch

CURRENT="$(git rev-parse --abbrev-ref HEAD)"

# find where the current branch branched from origin/master
REFERENCE="origin/master"
BRANCH_POINT="$(git merge-base "$REFERENCE" HEAD)"
# from https://stackoverflow.com/a/4991675/308930
BRANCH_POINT="$(diff -u <(git rev-list --first-parent HEAD) <(git rev-list --first-parent "$REFERENCE") | sed -ne 's/^ //p' | head -1)"

function oldestCommit() {
    base="$1"
    topic="$2"
    git cherry "$topic" "$base" | sed -e '/^+ /{s/^+ //;p;};d' | xargs -n1 git log -1 --pretty=tformat:"%at %H" | sort | head -n1 | cut -d' ' -f2
}

function newestCommit() {
    revisionRange="$1"
    git log --pretty=format:"%at %H" "$revisionRange" | sort -r | head -n1 | cut -d' ' -f2
}

OLDEST="$(oldestCommit "$REFERENCE" HEAD)"
TIME_OF_BRANCH="$(git log -1 --pretty=format:%at "$OLDEST")"
HUMAN_TIME_OF_BRANCH="$(git log -1 --pretty=format:%ai "$OLDEST")"

echo
echo "Current branch $CURRENT:"
echo "    Branched from $REFERENCE at $BRANCH_POINT"

echo
echo "The following branches (newer than $HUMAN_TIME_OF_BRANCH) have conflicts with $CURRENT:"

function authors() {
    revisionRange="$1"
    git log "$revisionRange" --pretty=format:%an | sort | uniq | paste -s -d',' - | sed -e 's/,/, /g'
}

function showConflicts() {
    BASE="$1"
    A="$2"
    B="$3"
    if git merge-tree "$(git merge-base "$A" "$B")" "$A" "$B" | grep "^changed in both" > /dev/null; then
        echo
        echo "$i"
        AUTHORS=$(authors "$REFERENCE".."$A")
        echo "    $AUTHORS"
        git merge-tree "$(git merge-base "$A" "$B")" "$A" "$B" | sed -e "/^changed in both/{N;s/.*\\n//;p;};d" | cut -b 58- | cat -n
    fi
}

for i in $(git branch -r | grep -v ' -> '); do
    # It would be ideal to find the time of the newest commit on the branch
    # instead of the time of the commit at the head of the branch,
    # but doing that makes the script too slow;
    # is there a faster way to implements newestCommit?
    # NEWEST="$(newestCommit "$REFERENCE".."$i")"
    TIME_OF_I="$(git log -1 --pretty=format:%at "$i")"
    if [ "$TIME_OF_I" -ge "$TIME_OF_BRANCH" ]; then
        showConflicts "$REFERENCE" "$i" HEAD
    fi
done