bug#11378: 24.1.50; Suggestion: Let M-i in isearch cycle `search-invisible'

[Juri Linkov]

> I understand that approach.  I disagree, that's all.

It's no surprise that you disagree because both preferences make sense:

(1) Start each new search afresh with default values.

(2) Keep the current search state for subsequent searches.

There are more possible preferences:

(3) Someone even might prefer to keep the current search state
    within the confines of the current buffer (easy to do with
    `make-local-variable' on the transient search variables).

(4) Reuse the previous search values only for the repeated search
    `C-s C-s'.  This what the variable `isearch-last-case-fold-search'
    is used for.  But why `isearch-last-case-fold-search' only?
    Other search variables could be supported too.

This suggests two new customizable options: one to define which search
variables to keep for the next search to be able to choose the behavior
between (1) and (2) for every search variable, and another option for (4)
to choose which search variables to keep for the repeated search `C-s C-s'
(its default value could reuse the last case-fold only as it currently does).