Function source_walker 

pub fn source_walker(source: &Utf8Path) -> WalkBuilder

Build a source-tree walker that skips repo plumbing.

Excluded directory names anywhere in the tree:

• .yui/ — yui’s own state and backup mirror; can grow huge.
• .git/ — git plumbing of the dotfiles repo itself. The check is on the basename, so a home/.config/git/ (note: no leading dot) inside the dotfiles is NOT excluded — only the literal .git.

git_ignore(false) / ignore(false) keep .gitignore / .ignore rules from swallowing 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.