Add `flymake-inhibit', etc.

Should make this a package.

init.el

@@ -937,7 +937,53 @@ successive invocations."
            "C-c l v" #'find-variable))
 
 (setup flymake
-  (:hook-into prog-mode)
+
+  (defvar flymake-inhibit-major-modes nil
+    "Which major-modes NOT to enable `flymake' in.")
+
+  (defvar flymake-inhibit-file-name-regexps '("init\\.el\\'"
+                                              "early-init\\.el\\'")
+    "List of file regexps NOT to enable `flymake' in.")
+
+  (defvar flymake-inhibit-buffer-name-regexps (list (rx "*scratch*"))
+    "List of buffer-name regexps NOT to enable `flymake' in.")
+
+  (defun list-string-match-p (string regexp-list)
+    "Return t if at least one regex in RETGEXP-LIST matches STRING, else nil."
+    (when string                        ; if STRING is nil, return nil.
+      (catch 'found
+        (dolist (regexp regexp-list)
+          (when (string-match regexp string)
+            (throw 'found t))))))
+
+  (defun flymake-unless ()
+    "Turn on `flymake-mode', UNLESS it's inhibited.
+There are three methods to inhibit flymake in a file.  From most
+specific to most general, they are these:
+
+- `flymake-inhibit': a file-local-variable
+
+- `flymake-inhibit-buffer-name-regexps': a list of regexps to
+  match the buffer name against.  If one of them matches, inhibit
+  `flymake-mode'.
+
+- `flymake-inhibit-file-name-regexps': a list of regexps to match
+  the filename against.  If one of them matches, inhibit
+  `flymake-mode'.
+
+- `flymake-inhibit-major-modes': a list of major-modes in which
+  to inhibit `flymake-mode'.  Really only useful if you want to
+  generally add `flymake-mode' to `prog-mode-hook'."
+    (unless (or (bound-and-true-p flymake-inhibit) ; file-local variable
+                (list-string-match-p (buffer-name)
+                                     flymake-inhibit-buffer-name-regexps)
+                (list-string-match-p (buffer-file-name)
+                                     flymake-inhibit-file-name-regexps)
+                (apply #'derived-mode-p flymake-inhibit-major-modes))
+      (flymake-mode-on)))
+
+  (add-hook 'prog-mode-hook #'flymake-unless)
+  
   (:bind "M-n" #'flymake-goto-next-error
          "M-p" #'flymake-goto-prev-error))