Comment by vkoskiv | Hacker News Reader

Comment by vkoskiv | Hacker News Reader

I too just discovered these a few days ago! I've been trying to work out a satisfactory way to combine multiple repositories into a monorepo at work. Since I'm building a new repo, I'm free to rewrite history, so I've used `git-filter-branch` to modify the sub-repositories into a form suitable for merging (moved all files to subdirectories, matching the final monorepo structure). Merging them with `--allow-unrelated-histories` is... Okay. No conflicts, the linear git log looks good, and I also prepended the module name to commit messages before merging, so it reads well. But the graph is super ugly (Merges with many years of commits in between, because I just merged the repos in one by one). What I'd really like to do is to "zip" all the histories together into a single, linear history, with all the commits in chronological order. Thus far I haven't found a way to do this with git. I'm probably missing some obvious reason why that couldn't work, but I haven't come up with any.

Funny, I did just exactly that at work yesterday. If your branches have linear histories, here's what to do:

1. Make sure all branches touch separate files. I would strongly recommend git-filter-repo over git-filter-branch. It's way simpler to use and orders of magnitudes faster.

2. Generate the list of commits in the correct order:

git rev-list --date-order --reverse branchA BranchB BranchC > revisions.txt

3. Go to any branch and: git rebase -i --root --force-rebase

Paste the contents of revisions.txt into the sequence editor and add "p " at the bigging of every line. Run the rebase and you are done.

Thank you! This looks like exactly what I want. I actually am already using `git-filter-repo` - I just confused the two names in my comment there. Super useful tool!

I figured out a way to not have to paste in manually to the sequence editor. I wrote a script like this:

-----

#!/bin/bash

if [[ ! -f "$1" ]]; then

exit 1

fi

git rev-list --no-merges --date-order --reverse $(git branch -a | grep -v '*' | grep master) | awk '{print "p " $0}' > $1

exit 0

-----

Then I can just:

-----

pushd monorepo

GIT_SEQUENCE_EDITOR=../inject_reflist.sh git rebase -i --root --force-rebase

popd

-----

And off we go! Apparently there were a few branches + merges, and we have some ongoing feature branches, so I need to find a way to bring in branches other than master as well, preferably while conserving the merges as-is, instead of skipping them like I do above.

Have you seen reposurgeon? It’s not something I’ve personally used, but it might be able to help you out!

http://www.catb.org/esr/reposurgeon/

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