opnsense-src/tools/tools/git/HOWTO

This directory contains tools intended to help committers use git when
interacting with standard FreeBSD project resources like Differential.

I. arcgit

arcgit is a wrapper script around the arc command line tool that simplifies the
automatic creation of a series of Differential reviews from a series of git
commits.  The intended workflow is:

1. Create a series of commits in git.  Each commit will be a separate review, so
   try to make each commit as self-contained as possible.  The series of commits
   should demonstrate a logical progression towards your end goal.  For example,
   one commit might refactor existing code to expose a new API without changing
   any current functionality.  A subsequent commit could then introduce your new
   code that uses the new API.

   It usually will not be helpful to present your code in the order in which it
   was actually written and can actually be harmful.  For example, if you
   introduced a bug early in your development process that you fixed in a
   subsequent commit, it is a waste of your reviewer's time to have them review
   old code with known bugs.  Instead, it would probably be best to squash the
   bug fix into the commit that introduced it, so that the bug is never
   presented to your reviewers in any review.

   The commit headline and commit message will be imported verbatim into
   Differential, so try to give each commit a meaningful commit message that
   gives your reviewers the necessary context to understand your change.

2. Create your reviews by running this command in your git repo:
     $ arcgit -r C1~..C2 -R reviewer -T testplan

   C1 should be the first commit that you want reviewed, and C2 should be the
   last commit that you want reviewed.  You may add multiple reviewers by
   specifying the -R option multiple times.  You can CC (AKA subscribe) people
   to a review with the -C option.  Note that if you subscribe a mailing list
   to a review, the mailing list will be emailed for every comment or change
   made to each review.  Please be judicious when subscribing mailing lists to
   reviews.  It may be better to instead send a single email to the appropriate
   list announcing all of the reviews and giving a short summary of the change
   as a whole, along with a link to the individual reviews.

3. When you need to make a change and upload it to a review, use the following
   process.  First, check out the branch corresponding to the review (arcgit
   automatically creates this branch for every review that it creates):

     $ git checkout review_D1234

   Next, make your change and perform whatever testing is necessary.  Commit it
   to your repository with this command:

     $ git commit --fixup HEAD

   You can upload the change to the code review by running this command in your
   repository while (ensure that you are still on the review_D1234 branch):

     $ arc diff --update D1234 review_D1234_base

   When you run arc, it will pull up your editor and give you a chance to
   change the message that will be shown in Differential for this upload.  It's
   recommended that you change it from the default "fixup! ...." as that does
   not give your reviewers an indication of what changes were made.  It's not
   recommended that you give the code review fixes meaningful commit messages
   directly because we will be using git's autosquash feature in the next step,
   which depends on the fixup! tag being present.

   Do not merge in other branches, or rebase your review branches at this point.
   Any changes that are made will show up in your reviews, and that will create
   extra noise that your reviewers will have to ignore.  If a reviewer requests
   a change that requires your commit to be based off of a later version of
   head, I would suggest deferring the change from the review and creating a
   new review with the change once you hit step 5.

4. Once the reviews have been approved, you need to prepare your patch series
   to be committed.  This involves squashing the fixes made in code review
   back into the original commit that they applied to.  This gives you a clean
   series of commits that are ready to be pushed to git.

   First, merge each of your review branches back into your main development
   branch.  For example:

     $ git checkout myfeature_dev
     $ for branch in review_D1234 review_D1235 review_D1236; do \
       git merge $branch || git mergetool -y || break; done

  Next, do an interactive rebase to squash your code review fixes back into the
  main commit:

    $ git rebase -i -k review_D1234_base

  review_D1234 should be the name of the *first* review that was created for
  you in step 2.  For every commit, your editor will be pulled up and you will
  be given one last chance to edit your commit message.  Make sure that you fill
  in the "Reviewed by:" tag indicating who accepted the review.  This would
  be a good point to add other tags like MFC after:, Sponsored by:, etc.

  The rebase will not introduce any actual changes to your code if done
  properly.  You can use this command to double-check that no changes were
  inadvertently made here:

    $ git diff myfeature_dev@{1}

5. Finally, you should get up to date with the latest changes from head:

    $ git pull --rebase origin master

  It is not recommended that you combine this step with the rebase done in the
  previous step.  The reason for this is that if you perform an interactive
  rebase that changes the commit that you branch from, it becomes much more
  difficult to use the reflog to confirm that the interactive rebase did not
  introduce unwanted changes.

  At this point, you are ready to commit your changes to head.  The importgit
  script can be used to import your commits directly into git.