Migrating patches from darcs to git
Suppose ghc/darcs is a darcs GHC tree containing patches that need to be migrated to git, and ghc/git is a git GHC tree.
This assumes that all your changes are in the ghc repo itself. Otherwise, if you have made changes to other repos (e.g. libraries/base) you'll need to do a similar procedure for those repos too.
We'll assume the following directory setup, where $root is some directory in your file system
- $root/my-darcs: the Darcs repo that contains the patches you'd like to move over into Git. We will make no changes to this repo.
- $root/baseline-git (initially non-existent): the Git repo at the moment of switchover
- $root/migrate (initially non-existent): during the transfer process this is going to be both a Darcs repo and a Git repo
Step 1: create migrate:
cd $root darcs get http://darcs.haskell.org/ghc mv ghc migrate
This gets a Darcs copy of the repo, precisely at the switchover point. (We don't need a tag, because the Darcs repos were frozen precisely at switchover, so the HEAD will do.)
Step 2: create baseline-git:
cd $root git clone http://darcs.haskell.org/ghc.git/ baseline-git cd baseline-git git checkout -b "some-descriptive-name" ghc-darcs-git-switchover
This gets a Git copy of the repo, precisely at the point of switchover (that's what the ghc-darcs-git-switchover tag does). At this moment all the source files in migrate and baseline-git should be bit-for-bit identical. Check this.
Step 3: make migrate/ into a Git repo too! All we need do is to copy over Git's meta-data.
cd $root/migrate mv ../baseline-git/.git .
Step 4: transfer patches. For each patch (or group thereof) you want to transfer, do this:
- Pull the patch into tmp-git:
cd $root/migrate darcs pull ../my-darcs ...interactively pull the patches you want...
- Record a Git patch for this patch group
git commit -a
Step 5: merge the patches into the git master:
git checkout master git merge "some-descriptive-name"
Step 6: validate and push to Git.