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 repository looks like:

src/
    http/
    math/
tests/
    http/
    math/

I want to create a new branch that only contains the src/math and tests/math directories.

If I run the following command:

git subtree split -P src/math -b math

It creates a branch that contains the contents of the src/math directory, but discards the src/math/ prefix.

If I try the same command with two directories:

git subtree split -P src/math -P tests/math -b math

It only extracts the contents of tests/math , ignoring src/math , and also discarding the tests/math prefix.

To summarize, I would like my final repository to look like:

src/
    math/
tests/
    math/

That is, keeping the original directory structure but discarding everything that's not explicitly mentioned in the command-line.

How can I do that?

Answer 1

Depending on your needs you might get away with git filter-branch .

I'm not entirely sure what you are trying to achieve, but if you merely want to have a repository with two directories removed (in the history?) this is probably your best shot.

See also Rewriting Git History .

$ git filter-branch --tree-filter 'rm -rf tests/http src/http' --prune-empty HEAD

This will look into each commit and remove the two directories from this commit. Be aware that this rewrites history (ie: alters your commit sha) and will cause headaches if you have a common history with another repository.

Answer 2

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, ie 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.

Source

Answer 3

Use git-filter-repo This is not part of git as of version 2.25. This requires Python3 (>=3.5) and git 2.22.0

git filter-repo --path src/math --path tests/math 

For my repo that contained ~12000 commits git-filter-branch took more than 24 hours and git-filter-repo took less than a minute.