query interprets repo revision "@" even after it's space separated

Created by: rvantonder

A query like repo:foo @thing now interprets the @thing part as a repo revision even though it's space separated. This means that some logic after query processing is making incorrect assumptions about whether a part of the query can be used as a revision. Likely a violation on the use of pattern in a repo rev context.

We should only be interpreting @rev if it is part of the repo value, not if it's space-separated.

If a user searches for any pattern starting with @, then they are likely to get the ugly message above (I ran into this searching for terms starting with @).