vim-patch:9.0.2098: No filetype support for xcompose files (#25983)

Problem:  No filetype support for xcompose files
Solution: Add filetype detection

closes: vim/vim#13508

4f9074b96c

runtime/ftplugin/xcompose.vim

@@ -0,0 +1,13 @@
+" Vim filetype plugin file
+" Language:	XCompose
+" Maintainer:	ObserverOfTime <chronobserver@disroot.org
+" Last Change:	2023 Nov 09
+
+if exists('b:did_ftplugin')
+  finish
+endif
+let b:did_ftplugin = 1
+
+setl comments=:# commentstring=#\ %s
+
+let b:undo_ftplugin = 'setl com< cms<'

runtime/lua/vim/filetype.lua

@@ -1521,6 +1521,8 @@ local filename = {
   wget2rc = 'wget2',
   ['.wvdialrc'] = 'wvdial',
   ['wvdial.conf'] = 'wvdial',
+  ['.XCompose'] = 'xcompose',
+  ['Compose'] = 'xcompose',
   ['.Xresources'] = 'xdefaults',
   ['.Xpdefaults'] = 'xdefaults',
   ['xdm-config'] = 'xdefaults',

runtime/syntax/xcompose.vim

@@ -0,0 +1,37 @@
+" Vim syntax file
+" Language:	XCompose
+" Maintainer:	ObserverOfTime <chronobserver@disroot.org>
+" Filenames:	.XCompose, Compose
+" Last Change:	2023 Nov 09
+
+" Comments
+syn keyword xcomposeTodo contained TODO FIXME XXX
+syn match xcomposeComment /#.*/ contains=xcomposeTodo
+
+" Includes
+syn keyword xcomposeInclude include nextgroup=xcomposeFile skipwhite
+syn match xcomposeFile /"\([^"]\|\\"\)\+"/ contained
+syn match xcomposeSubstitution /%[HLS]/ contained containedin=xcomposeFile
+
+" Modifiers
+syn keyword xcomposeModifier Ctrl Lock Caps Shift Alt Meta None
+syn match xcomposeModifierPrefix /\s*\zs[!~]\ze\s*/
+
+" Keysyms
+syn match xcomposeKeysym /<[A-Za-z0-9_]\+>/
+syn match xcomposeKeysym /[A-Za-z0-9_]\+/ contained
+syn match xcomposeString /"\([^"]\|\\"\)\+"/ contained nextgroup=xcomposeKeysym skipwhite
+syn match xcomposeColon /:/ nextgroup=xcomposeKeysym,xcomposeString skipwhite
+
+hi def link xcomposeColon Delimiter
+hi def link xcomposeComment Comment
+hi def link xcomposeFile String
+hi def link xcomposeInclude Include
+hi def link xcomposeKeysym Constant
+hi def link xcomposeModifier Function
+hi def link xcomposeModifierPrefix Operator
+hi def link xcomposeString String
+hi def link xcomposeSubstitution Special
+hi def link xcomposeTodo Todo
+
+let b:current_syntax = 'xcompose'

test/old/testdir/test_filetype.vim

@@ -721,6 +721,7 @@ func s:GetFilenameChecks() abort
     \ 'wsh': ['file.wsf', 'file.wsc'],
     \ 'wsml': ['file.wsml'],
     \ 'wvdial': ['wvdial.conf', '.wvdialrc'],
+    \ 'xcompose': ['.XCompose', 'Compose'],
     \ 'xdefaults': ['.Xdefaults', '.Xpdefaults', '.Xresources', 'xdm-config', 'file.ad', '/Xresources/file', '/app-defaults/file', 'Xresources', 'Xresources-file', 'any/Xresources/file', 'any/app-defaults/file'],
     \ 'xf86conf': ['xorg.conf', 'xorg.conf-4'],
     \ 'xhtml': ['file.xhtml', 'file.xht'],