Open Stack

I will take this opportunity to pimp the video series I did on this 
exact topic: 
https://www.youtube.com/watch?v=mHyvP7zp4Ko&list=PLR97FKPZ-mD9XJCfwDE5c-td9lZGIPfS5&index=4

On 12/5/18 11:18 AM, Eric Fried wrote:
> This started off as a response to some questions Sundar asked, but I
> thought it might be interesting/useful for new[er] OpenStack developers
> at large, so broadcasting.
> 
> I'm sure there's a document somewhere that covers this, but here's a
> quick run-down on how to develop multiple changes in a series. (Or at
> least, how I do it.)
> 
> Start on a freshly-pull'd master branch:
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ git checkout master
> Switched to branch 'master'
> Your branch is up-to-date with 'origin/master'.
> efried at efried-ThinkPad-W520:~/Neo/nova$ git pull --all
> <snip>
> 
> When you're working on a blueprint, you want to name your local branch
> after the blueprint. So in this case, bp/nova-cyborg-interaction.
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ git checkout -b
> bp/nova-cyborg-interaction
> Switched to a new branch 'bp/nova-cyborg-interaction'
> efried at efried-ThinkPad-W520:~/Neo/nova$ git log --oneline -1 --decorate
> 5bf6f63 (HEAD, origin/master, origin/HEAD, gerrit/master, master,
> bp/nova-cyborg-interaction) Merge "Deprecate the nova-xvpvncproxy service"
> 
> When you `git commit` (without `--amend`), you're creating a new commit
> on top of whatever commit you started at. If you started with a clean,
> freshly pull'd master branch, that'll be whatever the most recently
> merged commit in the master branch was. In this example, that's commit
> 5bf6f63.
> 
> So let's say I make an edit for my first patch and commit it:
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ echo 'python-cyborgclient>=1.0'
>>> requirements.txt
> efried at efried-ThinkPad-W520:~/Neo/nova$ echo 'python-cyborgclient==1.1'
>>> lower-constraints.txt
> efried at efried-ThinkPad-W520:~/Neo/nova$ git commit -a -m "Add cyborg
> client to requirements"
> [bp/nova-cyborg-interaction 1b2c453] Add cyborg client to requirements
>   2 files changed, 2 insertions(+)
> efried at efried-ThinkPad-W520:~/Neo/nova$ git log --oneline -2 --decorate
> 1b2c453 (HEAD, bp/nova-cyborg-interaction) Add cyborg client to requirements
> 5bf6f63 (origin/master, origin/HEAD, gerrit/master, master) Merge
> "Deprecate the nova-xvpvncproxy service"
> 
> I just made commit 1b2c453 on top of 5bf6f63. You'll notice my branch
> name (bp/nova-cyborg-interaction) came along with me.
> 
> Now I'm going to make another change, but just part of it, a
> work-in-progress commit:
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ mkdir nova/pci/cyborg
> efried at efried-ThinkPad-W520:~/Neo/nova$ touch nova/pci/cyborg/__init__.py
> efried at efried-ThinkPad-W520:~/Neo/nova$ git add nova/pci/cyborg/__init__.py
> efried at efried-ThinkPad-W520:~/Neo/nova$ git commit -m "WIP: Cyborg PCI
> handling"
> [bp/nova-cyborg-interaction ebb3505] WIP: Cyborg PCI handling
>   1 file changed, 0 insertions(+), 0 deletions(-)
>   create mode 100644 nova/pci/cyborg/__init__.py
> efried at efried-ThinkPad-W520:~/Neo/nova$ git log --oneline -3 --decorate
> ebb3505 (HEAD, bp/nova-cyborg-interaction) WIP: Cyborg PCI handling
> 1b2c453 Add cyborg client to requirements
> 5bf6f63 (origin/master, origin/HEAD, gerrit/master, master) Merge
> "Deprecate the nova-xvpvncproxy service"
> 
> Now commit ebb3505 is on top of 1b2c453, which is still on top of
> 5bf6f63 (the master). Note that my branch name came with me again.
> 
> At this point, I push my series up to gerrit. Note that it makes me
> confirm that I really want to push two commits at once.
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ git review
> You are about to submit multiple commits. This is expected if you are
> submitting a commit that is dependent on one or more in-review
> commits, or if you are submitting multiple self-contained but
> dependent changes. Otherwise you should consider squashing your
> changes into one commit before submitting (for indivisible changes) or
> submitting from separate branches (for independent changes).
> 
> The outstanding commits are:
> 
> ebb3505 (HEAD, bp/nova-cyborg-interaction) WIP: Cyborg PCI handling
> 1b2c453 Add cyborg client to requirements
> 
> Do you really want to submit the above commits?
> Type 'yes' to confirm, other to cancel: yes
> remote:
> remote: Processing changes: new: 2, refs: 2 (\)
> remote: Processing changes: new: 2, refs: 2 (\)
> remote: Processing changes: new: 2, refs: 2 (\)
> remote: Processing changes: new: 2, refs: 2, done
> remote:
> remote: New Changes:
> remote:   https://review.openstack.org/623026 Add cyborg client to
> requirements
> remote:   https://review.openstack.org/623027 WIP: Cyborg PCI
> handling
> remote:
> To ssh://efried@review.openstack.org:29418/openstack/nova.git
>   * [new branch]      HEAD -> refs/publish/master/bp/nova-cyborg-interaction
> 
> Now if you go to either of those links - e.g.
> https://review.openstack.org/#/c/623026/ - you'll see that the patches
> are stacked up in series on the top right.
> 
> But oops, I made a mistake in my first commit. My lower constraint can't
> be higher than my minimum in requirements.txt. If I still had my branch
> locally, I could skip this next step, but as a matter of rigor to avoid
> some common pratfalls, I will pull the whole series afresh from gerrit
> by asking git review to grab the *top* change:
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ git review -d 623027
> Downloading refs/changes/27/623027/1 from gerrit
> Switched to branch "review/eric_fried/bp/nova-cyborg-interaction"
> 
> Now I'm sitting on the top change (which you'll notice happens to be
> exactly the same as before I pushed it - again, meaning I could
> technically have just worked from where I was, but see above):
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ git log --oneline -3 --decorate
> ebb3505 (HEAD, review/eric_fried/bp/nova-cyborg-interaction,
> bp/nova-cyborg-interaction) WIP: Cyborg PCI handling
> 1b2c453 Add cyborg client to requirements
> 5bf6f63 (origin/master, origin/HEAD, gerrit/master, master) Merge
> "Deprecate the nova-xvpvncproxy service"
> 
> But I want to edit 1b2c453, while leaving ebb3505 properly stacked on
> top of it. Here I use a tool called `git restack` (run `pip install
> git-restack` to install it).
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ git restack
> 
> This pops me into an editor showing me all the commits between wherever
> I am and the main branch (now they're in top-first order):
> 
> pick 1b2c453 Add cyborg client to requirements
> pick ebb3505 WIP: Cyborg PCI handling
> <snip>
> 
> I want to fix the first one, so I change to:
> 
> edit 1b2c453 Add cyborg client to requirements
> pick ebb3505 WIP: Cyborg PCI handling
> <snip>
> 
> Save and quit the editor, and I see:
> 
> Stopped at 1b2c453453242a3fa57f2d4fdc80c837b02b804f... Add cyborg client
> to requirements
> You can amend the commit now, with
> 
>          git commit --amend
> 
> Once you are satisfied with your changes, run
> 
>          git rebase --continue
> 
> I fix lower-constraints:
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ sed -i
> 's/cyborgclient==1.1/cyborgclient==1.0/' lower-constraints.txt
> 
> ...and *amend* the current commit
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ git commit -a --amend --no-edit
> [detached HEAD 6b3455f] Add cyborg client to requirements
>   Date: Wed Dec 5 09:43:15 2018 -0600
>   2 files changed, 2 insertions(+)
> 
> ...and tell `git restack` to proceed
> 
> efried at efried-ThinkPad-W520:~/Neo/nova$ git rebase --continue
> Successfully rebased and updated
> refs/heads/review/eric_fried/bp/nova-cyborg-interaction.
> 
> If I had a taller series, and I had changed 'pick' to 'edit' for more
> than one commit, I would now be sitting on the next one I needed to
> edit. As it is, that was the only thing I needed to do, so I'm done and
> sitting on the top of my series again.
> 
> 124b612 (HEAD, review/eric_fried/bp/nova-cyborg-interaction) WIP: Cyborg
> PCI handling
> 6b3455f Add cyborg client to requirements
> 5bf6f63 (origin/master, origin/HEAD, gerrit/master, master) Merge
> "Deprecate the nova-xvpvncproxy service"
> 
> Notice that the commit hashes have changed for *both* commits (but not
> the master). The top one changed because it got rebased onto the new
> version of the middle one.
> 
> Now if I push the series back up to gerrit, I get the same confirmation
> prompt, and both changes get a new patch set. If you look at the top
> patch in gerrit, you'll see that PS2 shows up as just a rebase.
> 
> 
> ====================
> 
> That ought to be enough for now. There's a couple of gotchas when
> restacking and the automatic rebase results in merge conflicts, but we
> can save that for another time.
> 
> To answer your specific question:
> 
>> * If you have a patch sequence A followed by B, where patch B depends
> on patch A,
>>    how do you communicate that in the submission?
> 
> If they're in the same commit series, like the example above, It Just
> Happens. Zuul and the CIs know to pull the whole series when they run;
> gerrit won't merge N+1 until N is merged; etc.
> 
> If they're *not* in the same commit series, or if they're not in the
> same repository, you can use Depends-On in the commit message, to the
> same effect.  (But I'm not sure if/how Depends-On works for feature
> branches.)
> 
> HTH,
> efried
> .
> 
>