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From: Jonathan Nieder <jrnieder@gmail.com>
To: Stefan Beller <sbeller@google.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 5/5] submodule: submodule_move_head omits old argument in forced case
Date: Tue, 19 Dec 2017 14:44:31 -0800
Message-ID: <20171219224431.GG240141@aiede.mtv.corp.google.com> (raw)
In-Reply-To: <20171219222636.216001-6-sbeller@google.com>

Hi,

I had trouble understanding what this fixes, so I'll try nitpicking a
bit as a sideways way to address that.

Stefan Beller wrote:

> With the previous patch applied (fix of the same() function),

This tripped me up a bit.  Usually commits assume that all previous
patches have already been applied, since that allows the maintainer to
apply the early part of a series on one day and the later part another
day without losing too much context.

I think this intends to say something like

	Now that we allow recursing into an unchanged submodule (see
	"unpack-trees: Fix same() for submodules", 2017-12-19), it is
	possible for ...

>                                                               the
> function `submodule_move_head` may be invoked with the same argument
> for the `old` and `new` state of a submodule, for example when you
> run `reset --hard --recurse-submodules` in the superproject that has no
> change in the gitlink entry, but only worktree related change in the
> submodule. The read-tree call in the submodule is not amused about
> the duplicate argument.

What is the symptom of read-tree being unamused?  Is that a sign that
these patches are out of order (i.e. that we should prepare to handle an
unchanged submodule first, and then adjust the caller to pass in
unchanged submodules)?

> It turns out that we can omit the duplicate old argument in all forced
> cases anyway, so let's do that.

What is the end-user visibile effect of such a change?  E.g. what
becomes possible to a user that wasn't possible before?

Among the commands you mentioned before:

  checkout -f
	I think I would expect this not to touch a submodule that
	hasn't changed, since that would be consistent with its
	behavior on files that haven't changed.

  reset --hard
	Nice!  Yes, recursing into unchanged submodules is a big part
	of the psychological comfort of being able to say "you can
	always use reset --hard <commit> to get back to a known
	state".

  read-tree -u --reset
	This is essentially the plumbing equivalent of reset --hard,
	so it makes sense for them to be consistent.  Ok.

Based on the checkout -f case, if I've understood correctly then patch
4/5 goes too far on it (but I could easily be convinced otherwise).

> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>  submodule.c               | 4 +++-
>  t/lib-submodule-update.sh | 2 +-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/submodule.c b/submodule.c
> index fa25888783..db0f7ac51e 100644
> --- a/submodule.c
> +++ b/submodule.c
> @@ -1653,7 +1653,9 @@ int submodule_move_head(const char *path,
>  	else
>  		argv_array_push(&cp.args, "-m");
>  
> -	argv_array_push(&cp.args, old ? old : EMPTY_TREE_SHA1_HEX);
> +	if (!(flags & SUBMODULE_MOVE_HEAD_FORCE))
> +		argv_array_push(&cp.args, old ? old : EMPTY_TREE_SHA1_HEX);

Interesting.  What is the effect when old != new?

Thanks,
Jonathan

  reply index

Thread overview: 38+ messages in thread (expand / mbox.gz / Atom feed / [top])
2017-12-19 22:26 [PATCH 0/5] Fix --recurse-submodules for submodule worktree changes Stefan Beller
2017-12-19 22:26 ` [PATCH 1/5] t/lib-submodule-update.sh: clarify test Stefan Beller
2017-12-19 22:26 ` [PATCH 2/5] t/lib-submodule-update.sh: Fix test ignoring ignored files in submodules Stefan Beller
2017-12-22 19:34   ` Junio C Hamano
2017-12-27 19:27     ` Stefan Beller
2017-12-19 22:26 ` [PATCH 3/5] t/lib-submodule-update.sh: add new test for submodule internal change Stefan Beller
2017-12-19 22:31   ` Jonathan Nieder
2017-12-19 22:35     ` Stefan Beller
2017-12-19 22:26 ` [PATCH 4/5] unpack-trees: Fix same() for submodules Stefan Beller
2017-12-19 22:26 ` [PATCH 5/5] submodule: submodule_move_head omits old argument in forced case Stefan Beller
2017-12-19 22:44   ` Jonathan Nieder [this message]
2017-12-19 22:54     ` Stefan Beller
2017-12-19 23:15       ` Jonathan Nieder
2017-12-20  0:01       ` Jonathan Nieder
2017-12-20 19:36         ` Stefan Beller
2017-12-20 19:38           ` Stefan Beller
2017-12-27 22:57 ` [PATCHv2 0/5] Fix --recurse-submodules for submodule worktree changes Stefan Beller
2017-12-27 22:57   ` [PATCHv2 1/5] t/helper/test-lazy-name-hash: fix compilation Stefan Beller
2017-12-27 22:57   ` [PATCHv2 2/5] t/lib-submodule-update.sh: clarify test Stefan Beller
2017-12-27 22:57   ` [PATCHv2 3/5] t/lib-submodule-update.sh: Fix test ignoring ignored files in submodules Stefan Beller
2017-12-27 22:57   ` [PATCHv2 4/5] unpack-trees: oneway_merge to update submodules Stefan Beller
2018-01-02 19:43     ` Junio C Hamano
2018-01-02 23:04       ` Stefan Beller
2018-01-03  1:12       ` [PATCHv3 0/5] Fix --recurse-submodules for submodule worktree changes Stefan Beller
2018-01-03  1:12         ` [PATCH 1/5] t/helper/test-lazy-name-hash: fix compilation Stefan Beller
2018-01-03  1:12         ` [PATCH 2/5] t/lib-submodule-update.sh: clarify test Stefan Beller
2018-01-03  1:12         ` [PATCH 3/5] t/lib-submodule-update.sh: Fix test ignoring ignored files in submodules Stefan Beller
2018-01-03  1:12         ` [PATCH 4/5] unpack-trees: oneway_merge to update submodules Stefan Beller
2018-01-03  1:12         ` [PATCH 5/5] submodule: submodule_move_head omits old argument in forced case Stefan Beller
2018-01-03 20:49         ` [PATCHv3 0/5] Fix --recurse-submodules for submodule worktree changes Junio C Hamano
2018-01-03 21:16           ` Stefan Beller
2018-01-05 20:03           ` [PATCHv4 0/4] " Stefan Beller
2018-01-05 20:03             ` [PATCHv4 1/4] t/lib-submodule-update.sh: clarify test Stefan Beller
2018-01-05 20:03             ` [PATCHv4 2/4] t/lib-submodule-update.sh: Fix test ignoring ignored files in submodules Stefan Beller
2018-01-05 20:03             ` [PATCHv4 3/4] unpack-trees: oneway_merge to update submodules Stefan Beller
2018-01-05 20:03             ` [PATCHv4 4/4] submodule: submodule_move_head omits old argument in forced case Stefan Beller
2018-01-09 22:45             ` [PATCHv4 0/4] Fix --recurse-submodules for submodule worktree changes Junio C Hamano
2017-12-27 22:57   ` [PATCHv2 5/5] submodule: submodule_move_head omits old argument in forced case Stefan Beller

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