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Mar 20, 2013
I recently had the fun job of refactoring a large project that was spread across several Git repositories. Luckily, Git has some really useful tools for moving things around.
First, as an aside, a link to a useful page for anyone getting into some advanced Git work. Back when I started learning Git I found this explaination of Git Reset that totally expedited my understanding of Git.
Anyway, on with the post about moving Git branches around.
First merge into the master branch. We’re not only moving things around to new repos to improve the reuse across projects, we’re moving toward a feature branch strategy, rather than the stage/prod branching we had from this post.
Because of this, our current version of the code was on staging branch, and wanted to move over to the master branch. Merge into master branch, but avoid losing the branching information by using the –no-ff flag.
git merge --no-ff staging
You can delete remote branches, with
git push origin :staging
This removes the staging branch from origin (it’s ok the commit and branching history was retained thanks to the –no-ff merge option).
Then, as mentioned in this article, you add the original repo as a remote, adapt the command to pull from github. The -f fetches the commits…
git remote add -f other-project git@git...
Then prepare the sub-tree merge. Then actually read the sub tree over, applying prefix (i.e. put it in a sub folder).
Commit merge and push back up to GitHub.
As an aside: if you accidentally push a merge you can undo it with:
git revert -m 1 commit_hash
Now I want to move some stuff from one repo to another. But I don’t want the whole lot!. So, this time I clone a brand new copy - and remove everything I don’t want:
git clone... git filter-branch --subdirectory-filter dir_to_save -- -- all
That removes everything except dir_to_save, resulting in a clean repo with only files and history from dir_to_save.
Then I use the previous method to merge this remaining repo into the other repo. I’ll just repeat for good measure - don’t push back this temp repo - stuff has been removed and it only contains the stuff you don’t want to keep!