I have tried to run a local copy using a README on clojars-web: cloned, ran (migrate) in REPL, copied ~/.m2/repository into data/dev_repo, ran lein run -m clojars.tools.setup-dev, ran (run), and now I see a website with no packages.

all.edn is empty.

jars table in data/db is empty too. I suppose I need to pass some argument to setup-dev to point to repo?

Hmm, I have supplied a config using JAVA_TOOL_OPTIONS=-Dclojars.config.file=dev-resources/config.clj, now it indexed something.

Heh, I made it work, but it's not user-friendly. E.g. all releases uploaded yesterday: https://clojars.org/search?q=at%3A%5B1482255662000+TO+1482342072000%5D

The numbers are, obviously, Unix timestamps in milliseconds.

Syntax is straightforward Lucene.

Search is a Lucene query, so to make it better one has to traverse Query returned by Lucene parser and adjust all kinds of queries using field at. Not hard, but cumbersome.