Simple search should be a substring search

[madduck]

When a user searches for foo, I think they expect to be given results for files matching "foobar" too. Instead, matching a full word should be e.g. "foo".

[v6ak]

I can work on it. However, I'd like to ask first if this change of behavior would be accepted by the maintainer. (We might support both behaviors though configuration if we want to be conservative.)

[eikek]

I think the simple ("in names") search already does this (from the ui). If you look at the request, a search foo results in the api call with *foo*.