vim-patch:9.1.0953: filetype: APKBUILD files not correctly detected

Problem:  filetype: APKBUILD files not correctly detected
Solution: detect 'APKBUILD' files as apkbuild filetype,
          include a apkbuild syntax script (which basically
          just sources the sh.vim syntax file)
          (Hugo Osvaldo Barrera)

Vim plugins (e.g.: ALE, nvim-lspconfig, etc) rely on filetype to
determine which integrations/helpers are applicable. They expect
filetype=apkbuild for APKBUILD files.

On the other hand, plugins also enable bash-specific linters and
functionality when filetype=bash, but APKBUILD files are POSIX sh, not
bash, so these often provide bogus results.

Change the filetype for APKBUILD to a 'apkbuild', so that tools and
ftplugin can properly target these files. This filetype will use the
existing `sh` syntax rules, since these are applicable for them.

7cb24917a1

Co-authored-by: Hugo Osvaldo Barrera' via vim_dev <vim_dev@googlegroups.com>

runtime/lua/vim/filetype.lua

@@ -1439,6 +1439,7 @@ local filename = {
   ['/etc/asound.conf'] = 'alsaconf',
   ['build.xml'] = 'ant',
   ['.htaccess'] = 'apache',
+  APKBUILD = 'apkbuild',
   ['apt.conf'] = 'aptconf',
   ['/.aptitude/config'] = 'aptconf',
   ['=tagging-method'] = 'arch',
@@ -1798,7 +1799,6 @@ local filename = {
   ['.kshrc'] = detect.ksh,
   ['.profile'] = detect.sh,
   ['/etc/profile'] = detect.sh,
-  APKBUILD = detect.bash,
   PKGBUILD = detect.bash,
   ['.tcshrc'] = detect.tcsh,
   ['tcsh.login'] = detect.tcsh,

runtime/syntax/apkbuild.vim

@@ -0,0 +1,17 @@
+" Vim syntax file
+" Language:	apkbuild
+" Maintainer:	The Vim Project <https://github.com/vim/vim>
+" Last Change:	2024 Dec 22
+
+" quit when a syntax file was already loaded
+if exists("b:current_syntax")
+  finish
+endif
+
+" The actual syntax is in sh.vim and controlled by buffer-local variables.
+unlet! b:is_bash b:is_kornshell
+let b:is_sh = 1
+
+runtime! syntax/sh.vim
+
+let b:current_syntax = 'apkbuild'