Managing Pull Requests

The Apache Guacamole project requires code review for absolutely all changes, and uses pull requests to facilitate that review. However, because pull requests must be made against the read-only mirrors on GitHub, merging is slightly more complicated.

There is no “merge” button. Merges must be performed manually and pushed to the main repositories which live at the ASF. Once pushed, a robot running at the ASF (which has write access to the GitHub mirrors) will automatically close the pull request as merged.

You will need three remotes for each Apache Guacamole git repository:

  1. The upstream repository hosted by the ASF’s servers
  2. The GitHub mirror
  3. Your personal fork of the GitHub mirror

For the sake of simplicity, these will be referred to here as upstream, mirror, and origin, respectively. For example, the recommended configuration for incubator-guacamole-server would be:

$ git remote -v

After reviewing and approving code submitted via a pull request, you will need to:

  1. Manually fetch the contents of the pull request to a new branch via the command line:

    $ git fetch mirror pull/NUMBER/head:some-branch

    where NUMBER is the pull request number and some-branch is a sensible branch name of your choice.

  2. Ensure your copy of the base branch is up to date, whether that be master or the staging branch for an upcoming release:

    $ git fetch upstream
    $ git checkout master
    $ git merge --ff-only upstream/master
    $ git push origin
  3. Merge the branch containing the changes from the pull request:

    $ git merge --no-ff some-branch

    Be sure to specify --no-ff! Merges of pull requests must have corresponding merge commits, and the messages of those merge commits must properly tag the associated JIRA issue (just like all other commits).

  4. Confirm that the changes look as expected:

    $ git diff upstream/master
  5. Push the merge result to the ASF repository:

    $ git push upstream master

    You will be prompted for your username (Apache ID) and password. It is highly recommended that you not save/cache your credentials for this step, as it serves as an additional sanity check preventing accidental pushes to the main repository.

Once this is done, the ASF git bot should kick in, and emails should go out across the list noting each commit pushed. If this does not happen, or the commits show up only within the ASF repositories and not the GitHub mirrors, it may be necessary to reach out to Infra by opening an issue against the “Infrastructure” project in JIRA.

Merging release-specific changes

When a pull request is intended for a pending release, the merge base specified in the pull request should be the staging branch for that release. That said, part of the point of code review is to identify mistakes prior to merge, and using the wrong base for a release-specific change is one of those mistakes. It is good practice to verify whether a staging branch for the release exists in the main ASF repository, and to double-check whether the change in question is associated with a release-specific change by checking the “Fix Version” field for the issue in JIRA.

Merging release-specific changes involves:

  1. Merging the pull request to the staging branch. The steps for doing this are exactly as described above, except you will need to specify staging/VERSION instead of master.

  2. Merging the staging branch to master. Doing this is largely the same as described above, except that there is inherently no JIRA issue to tag in the commit message. A message like “Merging 0.9.10-incubating changes back to master.” is pretty sensible.

    DO NOT MERGE THE PULL REQUEST TO MASTER DIRECTLY! The point of merging the staging branch to master rather than the pull request is to ensure that the git history reflects that all commits to the staging branch are present on master. If the pull request is merged to master directly, then the git history ends up with two distinct merges and two distinct sets of commits, and final release sanity checks performed prior to deleting the staging branch will fail.