A script to merge repositories. Used in blog post (CZ) https://borekb.cz/2017/01/monorepo/. Updated version: https://gist.github.com/borekb/b4aa4f97ccd826dce1d4793a0d54fd26

merge-repos.sh

#!/bin/bash

# Merges child repo into target repo. Maintains branches and tags, filters history.
#
# Based on this amazing article: https://gofore.com/merge-multiple-git-repositories-one-retaining-history/ 


#---------------------------------
# Variables
#---------------------------------

TARGET_REPO='monorepo'
CHILD_REPO='microservice01'
NEW_PATH='subproject' # a subfolder in the target repo, `-` must be escaped as `\-`
BRANCH_TO_USE='123-merge-microservice01-repo'
TARGET_REPO_ISSUE='123'

RUN_CHILD_REPO_PROCESSING=true
RUN_REPO_MERGE=true


#---------------------------------
# Prepare the child repo
#---------------------------------

if [ "$RUN_CHILD_REPO_PROCESSING" = true ] ; then

cd $CHILD_REPO

# Create local branches
remote=origin ; for brname in `git branch -r | grep $remote | grep -v master | grep -v HEAD | awk '{gsub(/^[^\/]+\//,"",$1); print $1}'`; do git branch $brname $remote/$brname; done

# Remove remote branches (`/remotes/origin/*` refs)
git remote remove origin

# Filter the repo:
#   1. Move all files to a subdirectory named after the child repo. (Keeps branches and tags.)
#   2. Replaces [#123] with [versionpress/$CHILD_REPO#123].
#      Test this with: echo '#1 [#123] issue #2 other/repo#12 [other/repo#12]' | sed -r 's/( |\[|^)#([0-9]+)/\1versionpress\/CHILDREPO#\2/g'
git filter-branch --index-filter \
    'git ls-files -s | sed "s-\t\"*-&'$NEW_PATH'/-" |
    GIT_INDEX_FILE=$GIT_INDEX_FILE.new \
    git update-index --index-info &&
    mv "$GIT_INDEX_FILE.new" "$GIT_INDEX_FILE"
    ' --tag-name-filter cat --msg-filter 'sed -r '\''s/( |\[|^)#([0-9]+)/\1versionpress\/'$CHILD_REPO'#\2/g'\''' -f -- --all

# Clean up the `original` refs that Git keeps as a backup
git for-each-ref --format="%(refname)" refs/original/ | xargs -n 1 git update-ref -d

cd ..

fi

#---------------------------------
# Merge the repos
#---------------------------------

if [ "$RUN_REPO_MERGE" = true ] ; then

cd $TARGET_REPO
git checkout -b $BRANCH_TO_USE
git remote add -f $CHILD_REPO ../$CHILD_REPO
git merge --allow-unrelated-histories -m "[#$TARGET_REPO_ISSUE] Merge $CHILD_REPO repo" $CHILD_REPO/master
git remote rm $CHILD_REPO

fi

#---------------------------------
# Push
#---------------------------------

# After manually inspecting:
# git push origin $BRANCH_TO_USE

This Gist is used in the blog post https://borekb.cz/2017/01/monorepo/.

Updated version is here: https://gist.github.com/borekb/b4aa4f97ccd826dce1d4793a0d54fd26