Given that we now persist search/filter states even after a side context loses focus, we need to make it really
clear to the user that the context is currently being searched/filtered
This is a pickle: initially I wanted it so that a filter would cancel automatically if the current context lost focus.
But there are situations where you want to retain the focus, e.g. when a popup appears, or when you view the commits
of a branch. The issue is that when you view the commits of a branch, the branches context is removed from the context
stack. Even if this were not the case, you could imagine going branches -> sub-commits -> files -> sub-commits, where
in that case branches would definitely be off the stack upon navigating to the files context.
So because I'm too lazy to find a proper solution to this problem, I'm just making it so that filters in side contexts
are retained unless explicitly cancelled.
There's another edge case this commit handles which is that if I'm in the sub-commits context via the branches context
and start a search, then navigate to the reflog context and hit enter to get to the sub-commits context again, I need
to cancel the search before I switch. Likewise with the commit files context.
