Paths matching a pathlist entry are skipped by diff, status and checkout (DISABLE_PATHSPEC_MATCH) #7391

Reproduction steps

Two trees with foo-bar/c and foo/y, both files changed between them. Diff them with a pathlist:

char *paths[] = { "foo", "foo-bar/b" };

opts.flags = GIT_DIFF_DISABLE_PATHSPEC_MATCH;
opts.pathspec.strings = paths;
opts.pathspec.count = 2;

git_diff_tree_to_tree(&diff, repo, old_tree, new_tree, &opts);

Expected behavior

M foo/y, same as git diff-tree -r <old> <new> -- foo foo-bar/b.

Actual behavior

The diff is empty.

It looks like the problem is in iterator_pathlist_next_is. It bumps pathlist_walk_idx whenever some pathlist entry sorts before the path, even if that entry isn't the one at pathlist_walk_idx. At foo-bar/c, foo-bar/b sorts before it, so the index moves past foo, and foo/y never matches after that.

Tree and index iterators both go through this code, so it's not only diff. With the same two paths and pathlist:

• git_status_list with GIT_STATUS_OPT_DISABLE_PATHSPEC_MATCH, after changing both files in the workdir, reports foo/ as untracked. git status -- foo foo-bar/b shows M foo/y.
• git_checkout_tree of the new tree with paths and GIT_CHECKOUT_DISABLE_PATHSPEC_MATCH doesn't update foo/y. With GIT_CHECKOUT_FORCE it deletes foo/y from the workdir.

Version of libgit2 (release number or SHA1)

main (0551dfd)

Operating system(s) tested

Linux