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Git Tips (just a couple)

05 Jun

Below are a couple of git tips for the advanced git user. This is not meant to be remotely comprehensive in any way, just a couple of things I have figured out that I haven’t seen floating around out there yet.

Always rebase

At Grooveshark, we like to keep our history clean, such that the history of the main repo reflects when code was actually committed/accepted, regardless of when that code was written. As such, we almost always want to rebase. If you search for how to rebase by default, most of the advice you’ll find says to add the following to your ~/.gitconfig:

[branch]
    autosetuprebase = always

What this does, however, is it tells git to set up each branch to rebase as you create it. Any branch that git already knows about will not be set up to rebase; you’ll have to do that manually. Then in the future if you change your mind and decide you don’t want this functionality, you will have to remove it from each branch one by one. Instead put this in your ~/.gitconfig:

[pull]
    rebase = true

Now you’ve made the default behavior for pulling be to rebase. If you want to override that behavior for a particular branch, just set rebase = false in the .git/config file for the applicable repo, under the particular branch you want to do that for.

Github pull requests by the number

As mentioned earlier, when we do a pull request, we want it to be rebased onto the latest before it gets merged, so it’s a simple fast forward. Add the following to your ~/.gitconfig:

[alias]
    review = !sh -c 'REF=`git rev-parse --symbolic-full-name --abbrev-ref HEAD` && git fetch $1 $2:mergeReview -f && git checkout mergeReview && git rebase $REF && git checkout $REF && git diff HEAD..mergeReview' -
    pr = !git review origin refs/pull/$1/head
    approve = merge mergeReview

What’s going on here?
First we make a new command for reviewing arbitrary refs from arbitrary forks, called ‘review’. To use it, first checkout the target branch that you want to merge into, then run: ‘git review {remote} {ref}‘. Behind the scenes that fetches the remote ref into a temporary local branch called mergeReview, based on the remote ref you are reviewing. It rebases that onto the target branch you were in, switches you back to the target branch and then does a diff for you to review.
Next we make a new command for reviewing pull requests from github, called ‘pr’. This really just saves you from having to remember where github keeps pull request refs. It just calls git review and passes in the remote ref for the pull request.
Finally, ‘approve’ just merges the temporary mergeReview branch into the branch you’re currently in, which if you followed the instructions above is the target branch.

 

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