#!/bin/bash

# USE WITH CAUTION: this script re-writes history. You should be

# fully aware of the consequences: if you perform this job on

# a `pushed` commit, you will have to do a `push-force` to update.

# This means your collaborators will have to `pull-force`,

# potentially losing changes and breaking history.

((!$#)) && echo No commit hash provided, ignored && exit 1

COMMIT_TITLE=""

COMMIT_MSG=""

CHANGE_LIST=""

# Input: commit SHA

function commitMsg() {

# first line is the commit id, we don't need it

BASE=$(git rev-list --format=%B --max-count=1 $1 | tail -n +2)

# second line is the commit title

COMMIT_TITLE=$(echo "$BASE" | head -n 1)

# the rest is the commit message body (excluding the separator line break)

COMMIT_MSG=$(echo "$BASE" | tail -n +3)

}

# Input: commit SHA

function changeList() {

# Output is like:

# M a.txt

# A b.txt

# D c.txt

# R100 d.ttx d.txt

#

# Where M stands for "Modified" (git add),

# A stands for "Addition" (git add),

# D stands for "Deletion" (git rm),

# R100 stands for "Rename" (git mv), only with 100% matching

# we don't need the commit id at the first line.

CHANGE_LIST=$(git diff-tree --name-status --find-renames=1 --find-copies=1 -r --no-commit-id $1)

}

# Input: commit SHA

function editCommit() {

EDITOR="sed -i 's/pick $1/e $1/g'"

GIT_SEQUENCE_EDITOR="sed -i -e 's/^pick $1/edit $1/'" git rebase -i $1^ || exit 1

# re-playing events separately

echo "sed: '$GIT_SEQUENCE_EDITOR'"

}

# Input: nope

function unstage() {

echo "Unstaging..."

git reset --soft HEAD^

git reset HEAD

}

# Input: commit SHA

function replayEvents() {

while read -r -a line; do

CMD="${line[0]}"

ARG="${line[1]}"

ARG2="${line[2]}"

echo "Current line: '$line' -> '$CMD' '$ARG' '$ARG2'"

case $CMD in

# Modify

"M")

git add $ARG

;;

# Delete

"D")

git rm $ARG

;;

# Add

"A")

git add $ARG

;;

# Rename

"R"|"R1"|"R100")

# TODO: using git mv does not work great as ARG1 is already in "deleted" state, so it says "bad source"

# git mv $ARG $ARG2

git add $ARG2

git rm $ARG

;;

# default: not supported, abort

*)

echo "Command '$CMD' is not implemented, aborting"

git rebase --abort

exit -1

;;

esac

echo "Committing $line..."

MSG="$COMMIT_TITLE -> $CMD $ARG $ARG2

$COMMIT_MSG"

git commit --message "$MSG"

done <<< "$CHANGE_LIST"

git rebase --continue

echo "Done!"

}

commitMsg $1

changeList $1

echo "Commit title: '$COMMIT_TITLE'"

echo "Commit body: '$COMMIT_MSG'"

echo ""

echo "Processing split..."

echo "Changes: "

echo "'$CHANGE_LIST'"

editCommit $1

unstage

replayEvents $1

# abort in case of problem.

# If everything run fine we should have done `git rebase --continue`

git rebase --abort