tree af12fe958e606ce9cad97dc552f7a5cc15acd44e
parent b8f79fea99142c5025588ae7f1266e64884d0d3a
author Tom Pollard <tom.pollard@codethink.co.uk> 1556634357 +0100
committer Tom Pollard <tom.pollard@codethink.co.uk> 1557244119 +0100

element.py: Tweak pull_buildtrees logic in _pull_pending()

If an element is cached without a buildtree it not longer entails
that it may be possible to pull a buildtree for it, if it wasn't
cached with one at creation. Query _buildtree_exists() to reduce
possible redudant pull attempts.