Here’s the scenario:
I’ve got two repositories:
- github.com/example/web-app-backend.git
- github.com/example/web-app-frontend.git
I want to merge web-app-frontend into web-app-backend/html-src/ and keep the commit history.
Use git subtree
Ideally I’d like to completely interlace the commit histories as if they had always been in the same repo (like a rebase, which would require a --force push).
Unfortunately, there’s currently no simple way to interleave commits from multiple repositories by commit date, so a merge commit will have to do.
git clone https://github.com/example/web-app-backend.git ./web-app-backend/
pushd ./web-app-backend/
git checkout -b add-frontend
git subtree add -P html-src/ https://github.com/example/web-app-frontend.git master
What that looks like
If that all goes well you’ll see some output like this:
git fetch https://github.com/example/web-app-frontend.git master
From https://github.com/example/web-app-frontend.git
* branch master -> FETCH_HEAD
Added dir 'html-src'
And if you check git log, you’ll see a subtree merge commit:
git log
commit xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (HEAD -> add)
Merge: aaaaaaa bbbbbbb
Author: Jo Doe <jo@example.com>
Date: Mon Oct 19 11:01:39 2020 +0000
Add 'html-src/' from commit 'bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb'
git-subtree-dir: html-src
git-subtree-mainline: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
git-subtree-split: bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
If everything is to your liking, merge it back in to the mainstream:
git checkout master
git merge add-frontend
error: Invalid path
If you get an Invalid path error, it’s likely due to the use of ./.
git subtree add -P ./html-src/ https://github.com/example/web-app-frontend.git master
error: Invalid path './html-src/README.md'