threads / discuss / 49016

Squash & Merge Implementation

Subject: Squash & Merge Implementation

## tl;dr

3 messages between Aug 3, 2018 and Aug 3, 2018.

replies: 2people: 2as markdown or json

Vadim Belov· Aug 3, 2018, 12:01 UTC · lore

Hello, I'm trying to manually implement Github's *Squash&Merge *functionality. After looking many forums like stackoverflow.com I'm still struggling with the issue.

*The scenario is as follows*:
- master is a protected branch (configured on github)
- a service user *svc *is permitted to push to master (configured on github)
- other users don't have such permissions
- github PR status check is set to SUCCESS before execution of any set of
git commands below

1. This merges successfully without squash:
git checkout origin/master
git merge ${PR-Branch}
git push origin HEAD:master
git push origin --delete ${PR-Branch}

2. This closes the PR, but there is no update seen on master:
git checkout origin/master
git merge --squash --commit ${PR-Branch}
git push origin HEAD:master
git push origin --delete ${PR-Branch}

3. This fails to push to master with the error "GH006: Protected branch
update failed"  (despite that the PR is set to SUCCESS):
git checkout origin/master
git merge --squash ${PR-Branch}
git commit -am"comment"
git push origin HEAD:${m_mainBranch}
git push origin --delete ${m_prBranch}

Will appreciate your help on this.

Thanks, Vadim

Jeff King· Aug 3, 2018, 13:49 UTC · re: Vadim Belov · lore

Re: Squash & Merge Implementation

On Fri, Aug 03, 2018 at 03:01:15PM +0300, Vadim Belov wrote:

Show 5 quoted lines

> 1. This merges successfully without squash:
> git checkout origin/master
> git merge ${PR-Branch}
> git push origin HEAD:master
> git push origin --delete ${PR-Branch}

Right, this is a normal merge.

Show 5 quoted lines

> 2. This closes the PR, but there is no update seen on master:
> git checkout origin/master
> git merge --squash --commit ${PR-Branch}
> git push origin HEAD:master
> git push origin --delete ${PR-Branch}

Doing "merge --squash --commit" doesn't do what you expect; namely "--commit" does not override the non-committing nature of "--squash". It only override a "--no-commit" found elsewhere.

IMHO this is something that could be improved in Git (i.e., telling the difference between "the user did not say --no-commit" and "the user said --commit" and respecting it for --squash).

But that explains what you see. The push to master is a noop, since you didn't make a new commit. And then deleting the PR branch on GitHub auto-closes the PR.

Show 7 quoted lines

> 3. This fails to push to master with the error "GH006: Protected branch
> update failed"  (despite that the PR is set to SUCCESS):
> git checkout origin/master
> git merge --squash ${PR-Branch}
> git commit -am"comment"
> git push origin HEAD:${m_mainBranch}
> git push origin --delete ${m_prBranch}

So here you _do_ make an actual commit. But that commit doesn't look like a merge to the receiver; it just looks like a single commit that has all the changes there were on PR-Branch.

The tree of that commit should be the same tree that would result from a real merge. So in theory things like protected-branch status checks could handle that, but I suspect they use the actual commit id (the tree id is fine if you're just doing CI, but if you wanted to have a status check for commit messages, say, you'd obviously want that to be tied to the actual commit object).

I don't offhand recall how that is implemented (and you could also be falling afoul of other checks, like required reviews). But this is a GitHub-specific question, and you should probably ask GitHub support to go further.

-Peff

Vadim Belov· Aug 3, 2018, 17:23 UTC · re: Jeff King · lore

Re: Squash & Merge Implementation

Thanks, Peff!

I'm just doing the CI and the status check is for testing each commit to the PR-Branch. I'll try to get response from github on this as you suggested.

Thanks again, Vadim

On Fri, Aug 3, 2018 at 4:49 PM Jeff King <peff@peff.net> wrote:

Show 54 quoted lines

> On Fri, Aug 03, 2018 at 03:01:15PM +0300, Vadim Belov wrote:
>
> > 1. This merges successfully without squash:
> > git checkout origin/master
> > git merge ${PR-Branch}
> > git push origin HEAD:master
> > git push origin --delete ${PR-Branch}
>
> Right, this is a normal merge.
>
> > 2. This closes the PR, but there is no update seen on master:
> > git checkout origin/master
> > git merge --squash --commit ${PR-Branch}
> > git push origin HEAD:master
> > git push origin --delete ${PR-Branch}
>
> Doing "merge --squash --commit" doesn't do what you expect; namely
> "--commit" does not override the non-committing nature of "--squash". It
> only override a "--no-commit" found elsewhere.
>
> IMHO this is something that could be improved in Git (i.e., telling the
> difference between "the user did not say --no-commit" and "the user said
> --commit" and respecting it for --squash).
>
> But that explains what you see. The push to master is a noop, since you
> didn't make a new commit. And then deleting the PR branch on GitHub
> auto-closes the PR.
>
> > 3. This fails to push to master with the error "GH006: Protected branch
> > update failed"  (despite that the PR is set to SUCCESS):
> > git checkout origin/master
> > git merge --squash ${PR-Branch}
> > git commit -am"comment"
> > git push origin HEAD:${m_mainBranch}
> > git push origin --delete ${m_prBranch}
>
> So here you _do_ make an actual commit. But that commit doesn't look
> like a merge to the receiver; it just looks like a single commit that
> has all the changes there were on PR-Branch.
>
> The tree of that commit should be the same tree that would result from a
> real merge. So in theory things like protected-branch status checks
> could handle that, but I suspect they use the actual commit id (the tree
> id is fine if you're just doing CI, but if you wanted to have a status
> check for commit messages, say, you'd obviously want that to be tied to
> the actual commit object).
>
> I don't offhand recall how that is implemented (and you could also be
> falling afoul of other checks, like required reviews). But this is a
> GitHub-specific question, and you should probably ask GitHub support to
> go further.
>
> -Peff
>