Subject: Re: [PATCH v4] subtree: validate --prefix against commit in split

From: Junio C Hamano <[email-masked]>
Date: Tue, 03 Feb 2026 09:37:38 -0800

Pushkar Singh <[email-masked]> writes:

> Changes since v3:
> - Fix regression in existing subtree tests by checking prefix existence
>   with git cat-file instead of git ls-tree -d

OK, the check used to run

    git ls-tree -d "$rev" -- "$dir"

which (if I am reading this correctly) succeeded only when "$dir" is
an existing directory in "$rev".  Now you use

    git cat-file -e "$rev:$dir" 2>/dev/null

and this allows "$dir" to be a non-directory but say a blob.

> - Preserve original error message to keep test 17 passing

Ahh, OK.  I didn't check how the test was failing.  This message is
made to look like the error message we used to get much earlier
before calling cmd_split, and now cmd_split detects the condition to
give the error message, so it is better to match it.  Makes sense.

>  contrib/subtree/git-subtree.sh     |  9 +++++++++
>  contrib/subtree/t/t7900-subtree.sh | 22 ++++++++++++++++++++++
>  2 files changed, 31 insertions(+)
>
> diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
> index 17106d1a72..d7f9121f2f 100755
> --- a/contrib/subtree/git-subtree.sh
> +++ b/contrib/subtree/git-subtree.sh
> @@ -257,6 +257,9 @@ main () {
>  		test -e "$arg_prefix" &&
>  			die "fatal: prefix '$arg_prefix' already exists."
>  		;;
> +	split)
> +		# checked later against the commit, not the working tree
> +		;;
>  	*)
>  		test -e "$arg_prefix" ||
>  			die "fatal: '$arg_prefix' does not exist; use 'git subtree add'"
> @@ -966,6 +969,12 @@ cmd_split () {
>  	else
>  		die "fatal: you must provide exactly one revision, and optionally a repository.  Got: '$*'"
>  	fi
> +
> +	# Now validate prefix against the commit, not the working tree
> +	if ! git cat-file -e "$rev:$dir" 2>/dev/null
> +	then
> +		die "fatal: '$dir' does not exist; use 'git subtree add'"
> +	fi
>  	repository=""
>  	if test "$#" = 2
>  	then
> diff --git a/contrib/subtree/t/t7900-subtree.sh b/contrib/subtree/t/t7900-subtree.sh
> index 316dc5269e..e4f632f3af 100755
> --- a/contrib/subtree/t/t7900-subtree.sh
> +++ b/contrib/subtree/t/t7900-subtree.sh
> @@ -368,6 +368,28 @@ test_expect_success 'split requires path given by option --prefix must exist' '
>  	)
>  '
>  
> +test_expect_success 'split works when prefix exists in commit but not in working tree' '
> +	subtree_test_create_repo "$test_count" &&
> +	(
> +		cd "$test_count" &&
> +
> +		# create subtree
> +		mkdir pkg &&
> +		echo ok >pkg/file &&
> +		git add pkg &&
> +		git commit -m "add pkg" &&
> +		good=$(git rev-parse HEAD) &&
> +
> +		# remove it from working tree in later commit
> +		git rm -r pkg &&
> +		git commit -m "remove pkg" &&
> +
> +		# must still be able to split using the old commit
> +		git subtree split --prefix=pkg "$good" >out &&
> +		test -s out
> +	)
> +'
> +
>  test_expect_success 'split rejects flags for add' '
>  	subtree_test_create_repo "$test_count" &&
>  	subtree_test_create_repo "$test_count/sub proj" &&