Feature request description

Some users would like the ability to execute iterative queries. For example a search for repos matching some pattern. Then a subsequent search scoped within the context of the repos returned by the previous search for a separate regex pattern. In this way users can do an iterative filtering of results. This could be helpful for a variety of different programmatic applications and in some cases may be more comprehensible that a intersectional search using and or not to return the final results.

Is your feature request related to a problem? If so, please describe.

Not explicitly but it came about in a use case where users wanted to search for a set of repos containing a certain pattern but not containing matches to another pattern. In this case the not operator wasn't totally useful in that it matched any repo where any file matched the initial pattern and also excluded the not pattern. This isn't quite right.

patterntype:regexp select:repo pattern-1 not pattern-2

Describe alternatives you've considered.

You could accomplish something like this using search contexts but currently that UX is a little limited

Additional context

/cc @benvenker @lguychard