To manually collect cache entries, we need to know when a snapshot is
idle. Add a reference count in the form of a WaitGroup and keep track of
its uses. The pattern is that any time a snapshot is returned, it comes
with a release function that decrements the ref count.
Almost all uses of a snapshot originate in a user-facing request,
handled in beginFileRequest. There it's mostly an exercise in passing
Snapshots around instead of Views.
In the other places I took the path of least resistance. For file
modifications I tried to minimize the amount of code that needed to deal
with snapshots. For diagnostics I just acquired the snapshot at the
diagnostics call.
Change-Id: Id48a2df3acdd97f27d905e2c2be23072f28f196b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/241837
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
412b8bda49