pub fn absolute(path: &str) -> StringExpand description
convert a (possibly relative) file path to an absolute one
std::fs::canonicalize requires the path to exist; many callers hand
us paths that haven’t been resolved yet (e.g. \import{subdir}{f.sty}
constructs subdir/f.sty before find_file probes other dirs).
Mirror Perl’s Cwd::abs_path-style behavior: produce a lexically
absolute path joined against current_dir() when the input is
relative, then run it through our canonical() to collapse ./..
components.
Panics only if current_dir() itself fails — that means the cwd was
deleted out from under us, which we cannot safely resolve a relative
path against (and silently returning the input could let a relative
file reference target an attacker-controlled path).