serve: Fix problems with assets disappearing between servings. When an asset file changes, its source's pipeline is re-run. But that created a bake record that only had that pipeline's output, so the other outputs were incorrectly considered empty and therefore any stray files were removed. Now we copy over bake records for the pipelines we don't run.

[pytest]
norecursedirs = .* _darcs CVS .svn .git .hg *.egg-info dist build bower_components node_modules venv tmp* _cache {args}