[lehni]

patchAndFetchById(id, {}) and the other *AndFetch* methods returned undefined for an existing row when the patch was empty. Since 1.5.0, an update with nothing to write isn't run and resolves with 0, and the fetch read that 0 as "no rows matched".

An empty update now still fetches. As nothing was written, the fetch uses the find form of the update, the same query the static hooks get from asFindQuery(), so the row comes back only if it matches the update's filters, e.g. where() or the relation of $relatedQuery(). Updates that write something fetch by id as before, since a write can change the filtered columns. A builder onBuild() that selects columns applies to the fetch of an empty update; the fetch of a write copies only explicit select() calls, as before.

The find form had a bug of its own, also in asFindQuery() of static after hooks since 2.0.0: it was taken from the built write query, which already holds what the onBuild hooks of its context added, and they ran again when the find query was built, so e.g. a context join was added twice ("ambiguous column name"). The query now remembers which operations its context's onBuild hooks added during the build, and toFindQuery() leaves them out. toFindQuery() also clears the write's runAfter() callbacks, resolve value and fetched graph itself, which asFindQuery() did before, so both callers share it.

Tests cover patchAndFetchById(), updateAndFetchById(), $query().patchAndFetch() and a many-to-many $relatedQuery().patchAndFetchById(), each with a matching and a non-matching row, an empty patch with a joining context onBuild, and asFindQuery() in afterUpdate, afterInsert and afterDelete with a joining context onBuild (afterDelete not on SQLite, which can't delete with joins). They fail without the fix.

Closes #517