From: Junio C Hamano <gitster@pobox.com>
Date: Mon, 06 Jul 2026 14:44:10 GMT
Subject: Re: [PATCH 1/2] git-subtree: Bail out if we find output from Rust rewrite
Message-ID: <xmqqy0fob2kl.fsf@gitster.g>
In-Reply-To: <20260706115816.20267-2-ijackson@chiark.greenend.org.uk>

Ian Jackson <ijackson@chiark.greenend.org.uk> writes:

> +# Usage: reject_if_v2_config REV
> +#
> +# Bails if we find .git-subtree/config.  This file is used by the RIIR
> +# git-subtree, which can read data from this script, but which generates
> +# data that this script cannot cope with.  So if we find that the user's
> +# project has already been processed with the new tool, we stop, to
> +# avoid generating broken output.
> +reject_if_v2_config () {
> +	local config=.git-subtree/config
> +	if git rev-parse --verify -q "$rev:$config"; then
> +		die "fatal: tree contains $config: has been processed with new standalone (Rust) git-subtree; use that tool instead of this one.  See https://codeberg.org/diziet/git-subtree https://crates.io/crates/git-subtree"
> +	fi
> +}

[warning: I have no idea what is going on in the code we see here,
as I do not use subtree script at all]

The above helper may work for one caller that passes "$rev" but not
for the other caller that passes "HEAD", no?


	if git rev-parse --verify -q "$1:$config"
	then
		die "fatal: tree contains $config: has been processed with new standalone (Rust) git-subtree; use that tool instead of this one.  See https://codeberg.org/diziet/git-subtree https://crates.io/crates/git-subtree"
	fi

Overly long output does not look very easy to read, but I kept it
the same as the original.

> @@ -846,6 +860,7 @@ process_split_commit () {
>  #    Or: cmd_add REPOSITORY REF
>  cmd_add () {
>  
> +	reject_if_v2_config HEAD
>  	ensure_clean

If (global) $rev is not set here, we'd check :.git-subtree/config in
the index in order to detect the v2's configuration.  It seems to me
that this code however wants to inspect HEAD's tree.

> @@ -934,6 +949,8 @@ cmd_split () {
>  		die "fatal: you must provide exactly one revision, and optionally a repository.  Got: '$*'"
>  	fi
>  
> +	reject_if_v2_config "$rev"

This would happen to work, as the global "$rev" visible here is the
same one as what the new helper function sees and uses.

>  	# Now validate prefix against the commit, not the working tree
>  	if ! git cat-file -e "$rev:$dir" 2>/dev/null
>  	then
> @@ -1034,6 +1051,7 @@ cmd_merge () {
>  	then
>  		repository="$2"
>  	fi
> +	reject_if_v2_config HEAD
>  	ensure_clean

The same comment as the one for cmd_add's usage.

>  	if test -n "$arg_addmerge_squash"