Upsource lets you search the source code of any revision for files and text occurrences. In Java projects, you can find not just files but even specific classes or methods, both in the source code and in connected libraries.
You can search the entire repository from the project home page. To search within a specific revision, open that revision - the search is available in:
Type your query into the Go to symbol search field:
You can use lowerCamelHumps. For example, to find NonShortCircuitBooleanInspection, type
The search results include file names, source symbols, and text occurrences that contain the text you have entered in the field: