hideshow: Deep cleaning. (Bug#79934)

This is just a refactoring change, simplifying most of the code
and commentaries and removing/deprecating redundant code.

* etc/NEWS: Announce changes.
* lisp/progmodes/hideshow.el (hs-hide-hook, hs-show-hook): Use
'defcustom' instead of 'defvar'.
(hs-block-end-regexp, hs-forward-sexp-function)
(hs-adjust-block-beginning-function)
(hs-adjust-block-end-function, hs-find-block-beginning-function)
(hs-find-next-block-function)
(hs-looking-at-block-start-predicate)
(hs-inside-comment-predicate): Update docstring.
(hs-discard-overlays): Simplify.
(hs-life-goes-on): Update docstring.
(hs-hideable-region-p): Revert previous changes.
(hs-overlay-at): Simplify.
(hs-make-overlay): Fix performance.
(hs-block-positions): Rework.
(hs--add-indicators): Fix performance.
(hs-isearch-show-temporary): Simplify.
(hs-looking-at-block-start-p): Rename ...
(hs-looking-at-block-start-p--default): ... to this.
(hs-forward-sexp, hs-hide-comment-region): Mark as obsolete.
(hs-hide-block-at-point): Rework.
(hs-get-first-block): Rename ...
(hs-get-first-block-on-line): ... to this.
(hs-inside-comment-p--default): Rework.
(hs-find-block-beginning): Rename ...
(hs-find-block-beg-fn--default): ... to this.
(hs-find-next-block): Rename ...
(hs-find-next-block-fn--default): ... to this.
(hs-hide-level-recursive): Rework.
(hs-find-block-beginning-match): Remove function.
(hs-already-hidden-p): Simplify.
(hs-c-like-adjust-block-beginning): Mark as obsolete.
(hs-hide-all, hs-show-all, hs-hide-block, hs-show-block)
(hs-hide-level, hs-hide-initial-comment-block, hs-cycle):
Simplify.
* test/lisp/progmodes/hideshow-tests.el (hideshow-hide-level-1)
(hideshow-hide-level-2):
* test/lisp/progmodes/python-tests.el
(python-hideshow-hide-levels-3, python-hideshow-hide-levels-4):
* test/lisp/progmodes/hideshow-tests.el (hideshow-hide-level-1)
(hideshow-hide-level-2):
* test/lisp/progmodes/python-tests.el
(python-hideshow-hide-levels-3, python-hideshow-hide-levels-4):
Update tests.

etc/NEWS

@@ -1113,6 +1113,12 @@ blocks.
 *** New command 'hs-toggle-all'.
 This command hides or shows all the blocks in the current buffer.
 
+---
+*** 'hs-hide-level' no longer hide all the blocks in the current buffer.
+If 'hs-hide-level' was not inside a code block it would hide all the
+blocks in the buffer like 'hs-hide-all'.  Now it should only hide all
+the second level blocks.
+
 +++
 *** New user option 'hs-display-lines-hidden'.
 If this option is non-nil, Hideshow displays the number of hidden lines
@@ -1155,7 +1161,7 @@ after cursor position.  By default this is set to 'after-bol'.
 This user option controls the positions on the headline of hideable blocks
 where the 'TAB' key cycles the blocks' visibility.
 
-+++
+---
 *** The variable 'hs-special-modes-alist' is now obsolete.
 Instead of customizing Hideshow for a mode by setting the elements of
 'hs-special-modes-alist', such as START, COMMENT-START,

test/lisp/progmodes/hideshow-tests.el

@@ -246,7 +246,7 @@ sub()
      (should (string= (hideshow-tests-visible-string) contents)))))
 
 (ert-deftest hideshow-hide-level-1 ()
-  "Should hide 1st level blocks."
+  "Should hide 2st level blocks."
   (hideshow-tests-with-temp-buffer
    c-mode
    "
@@ -274,40 +274,6 @@ main(int argc, char **argv)
 
 \"String\"
 
-int
-main(int argc, char **argv)
-{}
-"))))
-
-(ert-deftest hideshow-hide-level-2 ()
-  "Should hide 2nd level blocks."
-  (hideshow-tests-with-temp-buffer
-   c-mode
-   "
-/*
-   Comments
-*/
-
-\"String\"
-
-int
-main(int argc, char **argv)
-{
-  if (argc > 1) {
-    printf(\"Hello\\n\");
-  }
-}
-"
-   (hs-hide-level 2)
-   (should (string=
-            (hideshow-tests-visible-string)
-            "
-/*
-   Comments
-*/
-
-\"String\"
-
 int
 main(int argc, char **argv)
 {

test/lisp/progmodes/python-tests.el

@@ -7428,7 +7428,7 @@ class SomeClass:
       (or enabled (hs-minor-mode -1)))))
 
 (ert-deftest python-hideshow-hide-levels-3 ()
-  "Should hide all blocks."
+  "Should hide 2nd level blocks."
   (python-tests-with-temp-buffer
    "
 def f():
@@ -7447,19 +7447,22 @@ def g():
      (python-tests-visible-string)
      "
 def f():
+    if 0:
 
 def g():
+    pass
 "))))
 
 (ert-deftest python-hideshow-hide-levels-4 ()
-  "Should hide 2nd level block."
+  "Should hide 3nd level block."
   (python-tests-with-temp-buffer
    "
 def f():
     if 0:
         l = [i for i in range(5)
              if i < 3]
-        abc = o.match(1, 2, 3)
+        if 1:
+            abc = o.match(1, 2, 3)
 
 def g():
     pass
@@ -7472,6 +7475,9 @@ def g():
      "
 def f():
     if 0:
+        l = [i for i in range(5)
+             if i < 3]
+        if 1:
 
 def g():
     pass