Re: [PATCH] clone: teach --single-branch and --branch during --recurse

From: Jeff King <peff@peff.net>
Date: Jan 9, 2020, 08:11 UTC
Message-ID: <20200109081150.GC3978837@coredump.intra.peff.net>
In-Reply-To: <20200108231900.192476-1-emilyshaffer@google.com>

On Wed, Jan 08, 2020 at 03:19:00PM -0800, Emily Shaffer wrote:

> Subject: clone: teach --single-branch and --branch during --recurse

A minor nit, but this subject confused me for a moment. I think we'd usually say "teach" for a new feature being implemented, and this is really just about passing along the existing features. Something like:

  clone: pass --single-branch and --branch when recursing submodules

would have been a bit more obvious (to me anyway).

> Previously, performing "git clone --recurse-submodules --single-branch"
> resulted in submodules cloning all branches even though the superproject
> cloned only one branch. Pipe --single-branch and its friend, --branch,
> through the submodule helper framework to make it to 'clone' later on.

Since I don't really use submodules, I don't have much data or even intuition to go on. But could this be a regression for some situations? E.g., imagine I have a repo "parent" whose branch "foo" has a submodule "child", but "child" only has a branch "bar". What happens now if I "git clone --recurse-submodules --single-branch -b foo parent", and what will happen after this patch?

I think it works before, but doesn't now.

Setting up like this:

  git init child
  (
  	cd child
  	git checkout -b bar
  	echo whatever >file
  	git add file
  	git commit -m 'child commit'
  )
  
  git init parent
  cd parent
  git checkout -b foo
  git submodule add $PWD/../child
  git commit -m 'add submodule'

if I use the current tip of master, I get:

  $ git clone --recurse-submodules --single-branch -b foo parent cur
  Cloning into 'cur'...
  done.
  Submodule 'child' (/home/peff/tmp/parent/../child) registered for path 'child'
  Cloning into '/home/peff/tmp/cur/child'...
  done.
  Submodule path 'child': checked out 'b5cbfcc9fec3b7d67e305468624fed2ba1aa4758'

  $ git -C cur/child log -1 --oneline | cat
  b5cbfcc child commit

with your patch, I get:

  $ git.compile clone --recurse-submodules --single-branch -b foo parent new
  Cloning into 'new'...
  done.
  Submodule 'child' (/home/peff/tmp/parent/../child) registered for path 'child'
  Cloning into '/home/peff/tmp/new/child'...
  warning: Could not find remote branch foo to clone.
  fatal: Remote branch foo not found in upstream origin
  fatal: clone of '/home/peff/tmp/parent/../child' into submodule path '/home/peff/tmp/new/child' failed
  Failed to clone 'child'. Retry scheduled
  Cloning into '/home/peff/tmp/new/child'...
  warning: Could not find remote branch foo to clone.
  fatal: Remote branch foo not found in upstream origin
  fatal: clone of '/home/peff/tmp/parent/../child' into submodule path '/home/peff/tmp/new/child' failed
  Failed to clone 'child' a second time, aborting

  $ git -C new/child log -1 --oneline | cat
  11acb3a add submodule

(there's nothing checked out in the submodule).

I have no idea how common this kind of thing would be, and I expect in most cases your patch would do what people want. But we might need to be better about retrying without those options when the first clone fails.

-Peff