There are several ways to setup Git for committers and contributors. Contributors can safely setup Git any way they choose but committers should take extra care since they can push new commits to the master at Apache and various policies there make backing out mistakes problematic. Therefore all but very small changes should go through a PR, even for committers. To keep the commit history clean take note of the use of –squash below when merging into apache/master.
This describes setup for one local repo and two remotes. It allows you to push the code on your machine to either your Github repo or to git-wip-us.apache.org. You will want to fork github’s apache/mahout to your own account on github, this will enable Pull Requests of your own. Cloning this fork locally will set up “origin” to point to your remote fork on github as the default remote. So if you perform “git push origin master” it will go to github.
To attach to the apache git repo do the following:
git remote add apache https://git-wip-us.apache.org/repos/asf/mahout.git
To check your remote setup
git remote -v
you should see something like this:
origin https://github.com/your-github-id/mahout.git (fetch) origin https://github.com/your-github-id/mahout.git (push) apache https://git-wip-us.apache.org/repos/asf/mahout.git (fetch) apache https://git-wip-us.apache.org/repos/asf/mahout.git (push)
Now if you want to experiment with a branch everything, by default, points to your github account because ‘origin’ is default. You can work as normal using only github until you are ready to merge with the apache remote. Some conventions will integrate with Apache Jira ticket numbers.
git checkout -b mahout-xxxx #xxxx typically is a Jira ticket number #do some work on the branch git commit -a -m "doing some work" git push origin mahout-xxxx # notice pushing to **origin** not **apache**
Once you are ready to commit to the apache remote you can merge and push them directly or better yet create a PR.
Push your branch to Github:
git checkout mahout-xxxx git push origin mahout-xxxx
Go to your mahout-xxxx branch on Github. Since you forked it from Github’s apache/mahout it will default any PR to go to apache/master.
When you are satisfied and want to push it to Apache’s remote repo proceed with Merging a PR
Create pull requests: .
Pull requests are made to apache/mahout repository on Github. In the Github UI you should pick the master branch to target the PR as described for committers. This will be reviewed and commented on so the merge is not automatic. This can be used for discussing a contributions in progress.
Start with reading  (merging locally).
Remember that pull requests are equivalent to a remote github branch with potentially a multitude of commits. In this case it is recommended to squash remote commit history to have one commit per issue, rather than merging in a multitude of contributor’s commits. In order to do that, as well as close the PR at the same time, it is recommended to use squash commits.
Merging pull requests are equivalent to a “pull” of a contributor’s branch:
git checkout master # switch to local master branch git pull apache master # fast-forward to current remote HEAD git pull --squash https://github.com/cuser/mahout cbranch # merge to master
–squash ensures all PR history is squashed into single commit, and allows committer to use his/her own
message. Read git help for merge or pull for more information about
--squash option. In this example we
assume that the contributor’s Github handle is “cuser” and the PR branch name is “cbranch”.
Next, resolve conflicts, if any, or ask a contributor to rebase on top of master, if PR went out of sync.
If you are ready to merge your own (committer’s) PR you probably only need to merge (not pull), since you have a local copy that you’ve been working on. This is the branch that you used to create the PR.
git checkout master # switch to local master branch git pull apache master # fast-forward to current remote HEAD git merge --squash mahout-xxxx
Remember to run regular patch checks, build with tests enabled, and change CHANGELOG.
If everything is fine, you now can commit the squashed request along the lines
git commit --author <contributor_email> -a -m "MAHOUT-XXXX description closes apache/mahout#ZZ"
MAHOUT-XXXX is all caps and where
ZZ is the pull request number on apache/mahout repository. Including
“closes apache/mahout#ZZ” will close the PR automatically. More information is found here .
Next, push to git-wip-us.a.o:
push apache master
(this will require Apache handle credentials).
The PR, once pushed, will get mirrored to github. To update your github version push there too:
push origin master
Note on squashing: Since squash discards remote branch history, repeated PRs from the same remote branch are difficult for merging. The workflow implies that every new PR starts with a new rebased branch. This is more important for contributors to know, rather than for committers, because if new PR is not mergeable, github would warn to begin with. Anyway, watch for dupe PRs (based on same source branches). This is a bad practice.
When we want to reject a PR (close without committing), we can just issue an empty commit on master’s HEAD without merging the PR:
git commit --allow-empty -m "closes apache/mahout#ZZ *Won't fix*" git push apache master
that should close PR
ZZ on github mirror without merging and any code modifications in the master repository.
Read . Comments and PRs with Mahout issue handles should post to mailing lists and Jira. Mahout issue handles must be in the form MAHOUT-YYYYY (all capitals). Usually it makes sense to file a jira issue first, and then create a PR with description
In this case all subsequent comments will automatically be copied to jira without having to mention jira issue explicitly in each comment of the PR.