Allow predicate based kernel checks in PacmanUpdates

PacmanUpdates previously supported either no kernel update detection or
matching a single kernel package name. That works for Arch's `linux`
package, but not for Manjaro's series specific kernel packages such as
`linux618` or `linux70`.

Replace the Bool indexed API with an explicit kernel check kind and add
`PacmanUpdatesPredicateK`, which accepts a `String -> Bool` predicate for
detecting kernel updates from the package list.

1 files changed, 33 insertions, 1 deletions

diff --git a/doc/plugins.org b/doc/plugins.org
index 442af34..4d14771 100644
--- a/doc/plugins.org
+++ b/doc/plugins.org
@@ -1367,7 +1367,7 @@
 
 *** =PacmanUpdates (Zero, One, Many, Error) Rate=
 
-  - *This constructor is deprecated. Use =PacmanUpdatesK= or =PacmanUpdatesNoK= instead.*
+  - *This constructor is deprecated. Use =PacmanUpdatesK=, =PacmanUpdatesPredicateK=, or =PacmanUpdatesNoK= instead.*
   - Aliases to =pacman=
   - =Zero=: a =String= to use when the system is up to date.
   - =One=: a =String= to use when only one update is available.
@@ -1407,6 +1407,38 @@
                     _ -> error "This is impossible"
     #+end_src
 
+*** =PacmanUpdatesPredicateK Rate IsKernelUpdate (Bool -> Either String (Int, Bool) -> String)=
+
+  - Aliases to =pacman=
+  - =IsKernelUpdate=: a =String -> Bool= predicate that receives each available
+    package name and returns =True= for kernel packages. This is useful for
+    distributions with versioned kernel package names, such as Manjaro's
+    =linux618= or =linux70= packages.
+  - =(Bool -> Either String (Int, Bool) -> String)=: a function producing the
+    string to be shown by the plugin; it is fed with a =Bool= telling whether
+    the running kernel is older than the installed kernel, and an =Int= and
+    =Bool= telling the number of available updates and whether one of them
+    matches the kernel predicate (or an error message if =checkupdates= fails).
+  - Example:
+    This example requires =import Data.Char (isDigit)= and
+    =import Data.List (stripPrefix)= in your configuration.
+    #+begin_src haskell
+      PacmanUpdatesPredicateK
+          600
+          ( \packageName ->
+              case stripPrefix "linux" packageName of
+                Just n -> not (null n) && all isDigit n
+                Nothing -> False
+          )
+          $ \oldKern mayb -> (if oldKern then "Running old kernel!" else "") ++
+                case mayb of
+                    Left _ -> "Some error occurred!"
+                    Right (0, False) -> "Up to date"
+                    Right (n, pendingK) | n >= 1 -> show n ++ " updates available"
+                                                  ++ if pendingK then " including a kernel update" else ""
+                    _ -> error "This is impossible"
+    #+end_src
+
 *** =PacmanUpdatesNoK Rate (Bool -> Either String Int -> String)=
 
   - Aliases to =pacman=