pub fn source_walker(source: &Utf8Path) -> WalkBuilderExpand description
Build a source-tree walker that skips yui’s internal .yui/ directory.
.yui/backup/ can grow huge over time, and .yui/rendered/ (future)
would also live here — neither is part of the user’s dotfiles, and
walking them slows render / list / absorb-find by a lot. We also keep
.gitignore / .ignore filtering disabled (git_ignore(false),
ignore(false)) so a user’s unrelated ignore rules don’t swallow
legitimate .tera / .yuilink files deeper in the tree.
.yuiignore is registered as a custom ignore filename so the
walker honours nested rules (every subdir that has a .yuiignore
adds its patterns scoped to that subtree, like git does with
.gitignore). The manual recursive walks in cmd.rs use the
YuiIgnoreStack companion type to get the same behaviour.