#!/bin/bash

# We need the TAB character for SED (Mac OS X sed does not understand \t)
TAB="$(printf '\t')"

function abort {
    echo "$(tput setaf 1)$1$(tput sgr0)"
    exit 1
}

function request_input {
    read -p "$(tput setaf 4)$1 $(tput sgr0)"
}

function request_confirmation {
    read -p "$(tput setaf 4)$1 (y/n) $(tput sgr0)"
    [ "$REPLY" == "y" ] || abort "Aborted!"
}


cat << "EOF"
This script rewrites your entire history, moving the current repository root
into a subdirectory. This can be useful if you want to merge a submodule into
its parent repository.

For example, your main repository might contain a submodule at the path src/lib/,
containing a file called "test.c".
If you would merge the submodule into the parent repository without further
modification, all the commits to "test.c" will have the path "/test.c", whereas
the file now actually lives in "src/lib/test.c".

If you rewrite your history using this script, adding "src/lib/" to the path
and the merging into the parent repository, all paths will be correct.

NOTE: This script might complete garble your repository, so PLEASE apply this
only to a clone of the repository where it does not matter if the repo is destroyed.

EOF

request_confirmation "Do you want to proceed?"

cat << "EOF"
Please provide the path which should be prepended to the current root. In the
above example, that would be "src/lib". Please note that the path MUST NOT contain
a trailing slash.

EOF

request_input "Please provide the desired path (e.g. 'src/lib'):"
# Escape input for SED, taken from http://stackoverflow.com/a/2705678/124257
TARGET_PATH=$(echo -n "$REPLY" | sed -e 's/[\/&]/\\&/g')


# Last confirmation
git ls-files -s | sed "s/${TAB}/${TAB}$TARGET_PATH\//"
request_confirmation "Please take a look at the printed file list. Does it look correct?"


# The actual processing happens here
CMD="git ls-files -s | sed \"s/${TAB}/${TAB}$TARGET_PATH\//\" | GIT_INDEX_FILE=\${GIT_INDEX_FILE}.new git update-index --index-info && mv \${GIT_INDEX_FILE}.new \${GIT_INDEX_FILE}"

git filter-branch \
    --index-filter "$CMD" \
    HEAD