Git subtree split two directories

Question

I\'ve been following this excellent answer to extract a subdirectory of my git repository into its own repository, while retaining the complete history.

My repositor

Answer 1

Use git-subtree add to split-in

# First create two *split-out* branches
cd /repos/repo-to-split
git subtree split --prefix=src/math --branch=math-src
git subtree split --prefix=test/math --branch=math-test

# Now create the new repo
mkdir /repos/math
cd /repos/math
git init

# This approach has a gotcha:
# You must commit something so "revision history begins",
# or `git subtree add` will complain about.
# In this example, an empty `.gitignore` is commited.
touch .gitignore
git add .gitignore
git commit -m "add empty .gitignore to allow using git-subtree"

# Finally, *split-in* the two branches
git subtree add --prefix=src/math ../repo-to-split math-src
git subtree add --prefix=test/math ../repo-to-split math-test

It worked for me with git --version 2.23.0. Also note that you can setup different prefixes at split-in time, i.e. add the src/math/ to src/ and test/math/ to test/.

Side note: use git log at the new repo before commiting to a remote, to see if resultant history is ok enought for you. In my case I have some commits with duplicated messages, because my repo history was so dirty, but it's ok for me.

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