Merging Multiple Git Repositories Into A MonoRepo

Note: Replace thing with your own repo name in the examples.

1. Create a repository which will store all your code

mkdir monorepo && cd monorepo
git init .
echo "# MonoRepo" > README.md
git add .
git commit -m "first commit"

2. Clone one of the existing repositories to a temporary location

Example Remote: ssh://git@code.company.com/thing.git

mkdir /tmp/thing
git clone ssh://git@code.company.com/thing.git /tmp/thing
cd /tmp/thing

3. Use git filter-branch to rewrite the history into a sub-directory.

Note: this step can take a very long time

export REPO_NAME="thing" 

git filter-branch -f --prune-empty --tree-filter '
    mkdir -p "$REPO_NAME"
    git ls-tree --name-only $GIT_COMMIT | xargs -I{} mv {} "$REPO_NAME"
'

4. Merge the rewritten repository into the monorepo

cd monorepo
git remote add thing /tmp/thing
git fetch thing
git merge thing/master

5. Clean up

git remote rm thing
rm -rf /tmp/thing

Here’s a script that performs all the steps

cd monorepo
./merge_repos.sh ssh://git@code.company.com/thing.git

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