Re: [PATCH 1/2] subtree: fix the GIT_EXEC_PATH sanity check to work on Windows

[Luke Shumaker <lukeshu@lukeshu.com>]

On Thu, 10 Jun 2021 03:13:30 -0600,
Johannes Schindelin via GitGitGadget wrote:
> 
> From: Johannes Schindelin <johannes.schindelin@gmx.de>
> 
> In 22d550749361 (subtree: don't fuss with PATH, 2021-04-27), `git
> subtree` was broken thoroughly on Windows.
> 
> The reason is that it assumes Unix semantics, where `PATH` is
> colon-separated, and it assumes that `$GIT_EXEC_PATH:` is a verbatim
> prefix of `$PATH`. Neither are true, the latter in particular because
> `GIT_EXEC_PATH` is a Windows-style path, while `PATH` is a Unix-style
> path list.
> 
> Let's keep the original spirit, and hack together something that
> unbreaks the logic on Windows.
> 
> A more thorough fix would look at the inode of `$GIT_EXEC_PATH` and of
> the first component of `$PATH`, to make sure that they are identical,
> but that is even trickier to do in a portable way.
> 
> This fixes https://github.com/git-for-windows/git/issues/3260
> 
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>  contrib/subtree/git-subtree.sh | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
> index b06782bc7955..6bd689a6bb92 100755
> --- a/contrib/subtree/git-subtree.sh
> +++ b/contrib/subtree/git-subtree.sh
> @@ -5,7 +5,13 @@
>  # Copyright (C) 2009 Avery Pennarun <apenwarr@gmail.com>
>  #
>  
> -if test -z "$GIT_EXEC_PATH" || test "${PATH#"${GIT_EXEC_PATH}:"}" = "$PATH" || ! test -f "$GIT_EXEC_PATH/git-sh-setup"
> +if test -z "$GIT_EXEC_PATH" || {
> +	test "${PATH#"${GIT_EXEC_PATH}:"}" = "$PATH" && {
> +		# On Windows, PATH might be Unix-style, GIT_EXEC_PATH not
> +		! type -p cygpath >/dev/null 2>&1 ||
> +		test "${PATH#$(cygpath -au "$GIT_EXEC_PATH"):}" = "$PATH"

Nit: That should have a couple more `"` in it:

    test "${PATH#"$(cygpath -au "$GIT_EXEC_PATH"):"}" = "$PATH"

But no need to re-roll for just that.

Do we also need to handle the reverse case, where PATH uses
backslashes but GIT_EXEC_PATH uses forward slashes?

-- 
Happy hacking,
~ Luke Shumaker