RE: isearch multiple buffers

[Drew Adams]

> I don't like the idea of making C-s in a buffer list buffer (ordinary
> or ibuffer) search into other buffers just because they are marked.

How about the suggestion that:

* C-s acts normally in Buffer List and Dired.

* Outside those buffers, C-s searches the buffers and file
  buffers that are marked in Buffer List and Dired

Isearch should provide some feedback, as already discussed, when it does a
multi-search, so that users are aware of what's happening.

The possible point of confusion will be for users who are unaware of the
connection between marking and isearch. The isearch doc would explain that,
but there is still room for confusion.

If that is thought to be too confusing, since users already have the habit
of marking buffers and files for other reasons, then perhaps a dedicated
mark could be used. Only users aware of this feature could then invoke it.