Re: Question relate to collaboration on git monorepo

>
> On Wed, Sep 21, 2022 at 8:22 AM ZheNing Hu <adlternative@gmail.com> wrote:
> >
> > Emily Shaffer <emilyshaffer@google.com> 于2022年9月21日周三 02:53写道：
> > >
> > > On Tue, Sep 20, 2022 at 5:42 AM ZheNing Hu <adlternative@gmail.com> wrote:
> > > >
> > > > Hey, guys,
> > > >
> > > > If two users of git monorepo are working on different sub project
> > > > /project1 and /project2 by partial-clone and sparse-checkout ,
> > > > if user one push first, then user two want to push too, he must
> > > > pull some blob which pushed by user one. I guess their repo size
> > > > will gradually increase by other's project's objects, so is there any way
> > > > to delete unnecessary blobs out of working project (sparse-checkout
> > > > filterspec), or just git pull don't really fetch these unnecessary blobs?
> > >
> > > This is exactly what the combination of partial clone and sparse
> > > checkout is for!
> > >
> > > Dev A is working on project1/, and excludes project2/ from her sparse
> > > filter; she also cloned with `--filter=blob:none`.
> > > Dev B is working on project2/, and excludes project1/ from his sparse
> > > filter, and similarly  is using blob:none partial clone filter.
> > >
> > > Assuming everybody is contributing by direct push, and not using a
> > > code review tool or something else which handles the push for them...
> > > Dev A finishes first, and pushes.
> > > Dev B needs to pull, like you say - but during that pull he doesn't
> > > need to fetch the objects in project1, because they're excluded by the
> > > combination of his partial clone filter and his sparse checkout
> > > pattern. The pull needs to happen because there is a new commit which
> > > Dev B's commit needs to treat as a parent, and so Dev B's client needs
> > > to know the ID of that commit.
> > >
> >
> > I don't agree here, it indeed fetches the blobs during git pull. So I
> > do a little
> > change in the previous test:
> >
> > (
> >   cd m2
> >   git cat-file --batch-check --batch-all-objects | grep blob | wc -l >
> > blob_count1
> > #  git push
> > #  git -c pull.rebase=false pull --no-edit #no conflict
> >   git fetch origin main
> >   git cat-file --batch-check --batch-all-objects | grep blob | wc -l >
> > blob_count2
> >   git merge --no-edit origin/main
> >   git cat-file --batch-check --batch-all-objects | grep blob | wc -l >
> > blob_count3
> >   printf "blob_count1=%s\n" $(cat blob_count1)
> >   printf "blob_count2=%s\n" $(cat blob_count2)
> >   printf "blob_count3=%s\n" $(cat blob_count3)
> > )
> >
> > warning: This repository uses promisor remotes. Some objects may not be loaded.
> > remote: Enumerating objects: 32, done.
> > remote: Counting objects: 100% (32/32), done.
> > remote: Compressing objects: 100% (20/20), done.
> > remote: Total 30 (delta 0), reused 0 (delta 0), pack-reused 0
> > Receiving objects: 100% (30/30), 2.61 KiB | 2.61 MiB/s, done.
> > From /Users/adl/./mono-repo
> >  * branch            main       -> FETCH_HEAD
> >    a6a17f2..16a8585  main       -> origin/main
> > warning: This repository uses promisor remotes. Some objects may not be loaded.
> > Merge made by the 'ort' strategy.
>
> Note: The merge completed successfully, and we see no evidence of
> additional blobs being downloaded before this point.
>

> > remote: Enumerating objects: 1, done.
> > remote: Counting objects: 100% (1/1), done.
> > remote: Total 1 (delta 0), reused 0 (delta 0), pack-reused 0
> > Receiving objects: 100% (1/1), 87 bytes | 87.00 KiB/s, done.
>
> Here, we do have an object download, which occurred after the merge
> completed, so there must be something happening after the merge which
> needs the extra blob; if we keep reading...
>
> >  project1/file1 | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
>
> Ah, the 'helpful' diffstat.  It downloads blobs from a promisor remote
> just so we can see what has changed, including in the area of the
> project we don't care about.
>
> (This is yet another reason it'd be nice to have a --restrict mode for
> grep/diff/log/etc. for sparse-checkout uses, and an ability to make it
> the default in some repo, so you could get just the diffstat within
> the region of the project that you care about.  We're discussing such
> an idea, but it isn't implemented yet.)
>
> > warning: This repository uses promisor remotes. Some objects may not be loaded.
> > blob_count1=11
> > blob_count2=11
> > blob_count3=12
> >
> > The result shows that blob count doesn't change in git fetch, but in git merge.
>
> If you add --no-stat to your merge command (or set merge.stat to
> false), the extra blob will not be downloaded.