Re: [GSoC][PATCH 09/13] submodule foreach: correct '$path' in nested submodules from a subdirectory

[Brandon Williams <bmwill@google.com>]

On 07/25, Prathamesh Chavan wrote:
> When running 'git submodule foreach' from a subdirectory of your
> repository, nested submodules get a bogus value for $sm_path:
> For a submodule 'sub' that contains a nested submodule 'nested',
> running 'git -C dir submodule foreach echo $path' would report
> path='../nested' for the nested submodule. The first part '../' is
> derived from the logic computing the relative path from $pwd to the
> root of the superproject. The second part is the submodule path inside
> the submodule. This value is of little use and is hard to document.
> 
> There are two different possible solutions that have more value:
> (a) The path value is documented as the path from the toplevel of the
>     superproject to the mount point of the submodule.
>     In this case we would want to have path='sub/nested'.
> 
> (b) As Ramsay noticed the documented value is wrong. For the non-nested
>     case the path is equal to the relative path from $pwd to the
>     submodules working directory. When following this model,
>     the expected value would be path='../sub/nested'.
> 
> The behavior for (b) was introduced in 091a6eb0fe (submodule: drop the
> top-level requirement, 2013-06-16) the intent for $path seemed to be
> relative to $cwd to the submodule worktree, but that did not work for
> nested submodules, as the intermittent submodules were not included in
> the path.
> 
> If we were to fix the meaning of the $path using (a) such that "path"
> is "the path from the toplevel of the superproject to the mount point
> of the submodule", we would break any existing submodule user that runs
> foreach from non-root of the superproject as the non-nested submodule
> '../sub' would change its path to 'sub'.
> 
> If we would fix the meaning of the $path using (b), such that "path"
> is "the relative path from $pwd to the submodule", then we would break
> any user that uses nested submodules (even from the root directory) as
> the 'nested' would become 'sub/nested'.
> 
> Both groups can be found in the wild.  The author has no data if one group
> outweighs the other by large margin, and offending each one seems equally
> bad at first.  However in the authors imagination it is better to go with
> (a) as running from a sub directory sounds like it is carried out
> by a human rather than by some automation task.  With a human on
> the keyboard the feedback loop is short and the changed behavior can be
> adapted to quickly unlike some automation that can break silently.

Great explanation, and I agree with going with choice (a).

> 
> Discussed-with: Ramsay Jones <ramsay@ramsayjones.plus.com>
> Signed-off-by: Prathamesh Chavan <pc44800@gmail.com>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>  git-submodule.sh             |  1 -
>  t/t7407-submodule-foreach.sh | 36 ++++++++++++++++++++++++++++++++++--
>  2 files changed, 34 insertions(+), 3 deletions(-)
> 
> diff --git a/git-submodule.sh b/git-submodule.sh
> index a427ddafd..493a64372 100755
> --- a/git-submodule.sh
> +++ b/git-submodule.sh
> @@ -320,7 +320,6 @@ cmd_foreach()
>  				prefix="$prefix$sm_path/"
>  				sanitize_submodule_env
>  				cd "$sm_path" &&
> -				sm_path=$(git submodule--helper relative-path "$sm_path" "$wt_prefix") &&
>  				# we make $path available to scripts ...
>  				path=$sm_path &&
>  				if test $# -eq 1
> diff --git a/t/t7407-submodule-foreach.sh b/t/t7407-submodule-foreach.sh
> index 6ba5daf42..0663622a4 100755
> --- a/t/t7407-submodule-foreach.sh
> +++ b/t/t7407-submodule-foreach.sh
> @@ -82,9 +82,9 @@ test_expect_success 'test basic "submodule foreach" usage' '
>  
>  cat >expect <<EOF
>  Entering '../sub1'
> -$pwd/clone-foo1-../sub1-$sub1sha1
> +$pwd/clone-foo1-sub1-$sub1sha1
>  Entering '../sub3'
> -$pwd/clone-foo3-../sub3-$sub3sha1
> +$pwd/clone-foo3-sub3-$sub3sha1
>  EOF
>  
>  test_expect_success 'test "submodule foreach" from subdirectory' '
> @@ -196,6 +196,38 @@ test_expect_success 'test messages from "foreach --recursive" from subdirectory'
>  	) &&
>  	test_i18ncmp expect actual
>  '
> +sub1sha1=$(cd clone2/sub1 && git rev-parse HEAD)
> +sub2sha1=$(cd clone2/sub2 && git rev-parse HEAD)
> +sub3sha1=$(cd clone2/sub3 && git rev-parse HEAD)
> +nested1sha1=$(cd clone2/nested1 && git rev-parse HEAD)
> +nested2sha1=$(cd clone2/nested1/nested2 && git rev-parse HEAD)
> +nested3sha1=$(cd clone2/nested1/nested2/nested3 && git rev-parse HEAD)
> +submodulesha1=$(cd clone2/nested1/nested2/nested3/submodule && git rev-parse HEAD)
> +
> +cat >expect <<EOF
> +Entering '../nested1'
> +$pwd/clone2-nested1-nested1-$nested1sha1
> +Entering '../nested1/nested2'
> +$pwd/clone2/nested1-nested2-nested2-$nested2sha1
> +Entering '../nested1/nested2/nested3'
> +$pwd/clone2/nested1/nested2-nested3-nested3-$nested3sha1
> +Entering '../nested1/nested2/nested3/submodule'
> +$pwd/clone2/nested1/nested2/nested3-submodule-submodule-$submodulesha1
> +Entering '../sub1'
> +$pwd/clone2-foo1-sub1-$sub1sha1
> +Entering '../sub2'
> +$pwd/clone2-foo2-sub2-$sub2sha1
> +Entering '../sub3'
> +$pwd/clone2-foo3-sub3-$sub3sha1
> +EOF
> +
> +test_expect_success 'test "submodule foreach --recursive" from subdirectory' '
> +	(
> +		cd clone2/untracked &&
> +		git submodule foreach --recursive "echo \$toplevel-\$name-\$sm_path-\$sha1" >../../actual
> +	) &&
> +	test_i18ncmp expect actual
> +'
>  
>  cat > expect <<EOF
>  nested1-nested1
> -- 
> 2.13.0
> 

-- 
Brandon Williams