[BUG] git-stash does not handle branch name with slash correctly

The default (commit) message when creating a stash strips the beginning of branch names if they contain a slash, e.g. "WIP on 3.2.x: …" instead of "WIP on stable/3.2.x: …"

 From builtin/stash.c (in do_create_stash):

	branch_ref = resolve_ref_unsafe("HEAD", 0, NULL, &flags);
	if (flags & REF_ISSYMREF)
		branch_name = strrchr(branch_ref, '/') + 1;

Whereas git-legacy-stash has this (in create_stash):

	if branch=$(git symbolic-ref -q HEAD)
	then
		branch=${branch#refs/heads/}
	else
		branch='(no branch)'
	fi
	msg=$(printf '%s: %s' "$branch" "$head")

I think it should also strip only "refs/heads/" or use another method that keeps the branch name intact.

(I have noticed this with a script/function that warns me when trying to pop a stash to another branch than where it was stashed from initially, which parses out the (original) branch name from this message.)

[System Info] git version: git version 2.33.1