-- Issue #244. A root's path could be stored with a trailing separator until
-- #243 normalised the incoming value. `roots::update` normalises the payload
-- and compares it against the stored value, so such a row never compares
-- equal: every edit, a policy change included, takes the relocation branch,
-- and there every planned destination is its own source. Normalising the
-- payload alone fixed the half that cannot bite; this is the other half.
--
-- `rtrim` strips every trailing separator at once, so '/mnt/x//' normalises
-- in one pass. A bare '/' rtrims to the empty string and is put back, which
-- is what `normalize_path` in arr-api does.
--
-- Guarded, because `roots.path` is UNIQUE and a migration that cannot apply
-- stops the daemon booting -- worse than the bug it fixes. A row is
-- normalised only when no other row shares its normalised path: neither a
-- row already holding the stripped value, nor another trailing-separator row
-- that would strip to the same thing. Every row in such a group is left
-- exactly as it is. That leaves two roots naming one directory, which is a
-- settings mistake for the operator to resolve by hand, not a reason to
-- refuse to boot.
--
-- This cannot introduce a collision either. An updated row's new value is a
-- normalised path no other row normalises to, and a row left alone whose raw
-- path equalled that value would have had the same normalised path, which is
-- the case the guard excludes.
UPDATE roots
SET path = CASE WHEN rtrim(path, '/') = '' THEN '/' ELSE rtrim(path, '/') END
WHERE path <> CASE WHEN rtrim(path, '/') = '' THEN '/' ELSE rtrim(path, '/') END
  AND NOT EXISTS (
      SELECT 1
      FROM roots AS other
      WHERE other.id <> roots.id
        AND CASE WHEN rtrim(other.path, '/') = '' THEN '/' ELSE rtrim(other.path, '/') END
            = CASE WHEN rtrim(roots.path, '/') = '' THEN '/' ELSE rtrim(roots.path, '/') END
  );