|Version 6 (modified by simonpj, 3 years ago) (diff)|
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. We're not going to try to preserve the history; just get the code into the repo.
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 checkout 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 ghc/git baseline-git cd baseline-git git checkout -b "some-descriptive-name" ghc-darcs-git-switchover
SLPJ: the clone command should mention the actual URL, not assuming you have a current copy. 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 ../baeline-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 git checkout master git merge "some-descriptive-name"
SLPJ: is this commit/checkout/merge thing right? Do you need to switch back to a branch for the next pull? Do you get to write a commit message?
Step 4: validate and push to Git.
First, make a backup of the darcs repo in case something goes wrong:
cp -a ghc/darcs ghc/backup-darcs
Now make sure ghc/darcs is fully up-to-date:
cd ghc/darcs ./darcs-all pull -a cd ../..
Next we checkout the git repo as it was at the darcs branch point:
git clone ghc/git ghc/migrate cd ghc/migrate git checkout -b "some-descriptive-name" ghc-darcs-git-switchover cd ../..
Now we put the git meta-data into our darcs repo, record the changes with git and merge them back to master:
cd ghc/darcs mv ../migrate/.git . git commit -a git checkout master git merge "some-descriptive-name" cd ../..
Finally, we pull the changes into our real git repo:
cd ghc/git git pull ../../ghc/darcs master
The ghc/migrate directory is no longer needed and can be removed.