rewrite_history_into.sh

#!/usr/bin/env bash

# Rewrite git history so that all filepaths are in a specific subdirectory
# You can use arguments for "git rev-list" to specify what commits to rewrite (defaults to rewriting history of the checked-out branch)
# All tags in the provided range will be rewritten as well
#
# Usage: rewrite_history_into.sh <subdirectory> [<rev-list-args>]
#
# Example: rewrite_history_into.sh packages/alpha
# Example: rewrite_history_into.sh main-repository --branches

SUBDIRECTORY=$1
REV_LIST_PARAMS=${@:2}
echo "Rewriting history into a subdirectory '$SUBDIRECTORY'"
# All paths in the index are prefixed with a subdirectory and the index is updated
# Previous index file is replaced by a new one (otherwise each file would be in the index twice)
# The tags are rewritten as well as commits (the "cat" command will use original name without any change)
SUBDIRECTORY_SED=${SUBDIRECTORY//-/\\-} TAB=$'\t' git filter-branch \
    --index-filter '
    git ls-files -s | sed "s-$TAB\"*-&$SUBDIRECTORY_SED/-" | GIT_INDEX_FILE=$GIT_INDEX_FILE.new git update-index --index-info && if [ -f "$GIT_INDEX_FILE.new" ]; then mv "$GIT_INDEX_FILE.new" "$GIT_INDEX_FILE"; fi' \
    --tag-name-filter 'cat' \
    -- $REV_LIST_PARAMS