runtime(lf): improve syntax script, add filetype plugin

- Greatly improve detection and highlighting of command/shell regions,
  input-device key labels, escape sequences (@joelim-work)
- Add ftplugin for formatoptions, toggling comment areas
  (@andis-sprinkis)
- Add a few missing lf option keywords, rm. old non-working code, misc.
  formatting (@andis-sprinkis)

closes: #17078

Signed-off-by: Andis Spriņķis <andis@sprinkis.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

.github/MAINTAINERS

@@ -222,6 +222,7 @@ runtime/ftplugin/ldapconf.vim		@ribru17
 runtime/ftplugin/leo.vim		@ribru17
 runtime/ftplugin/less.vim		@genoma
 runtime/ftplugin/lex.vim		@ribru17
+runtime/ftplugin/lf.vim			@andis-sprinkis
 runtime/ftplugin/liquid.vim		@tpope
 runtime/ftplugin/lua.vim		@dkearns
 runtime/ftplugin/lc.vim			@ribru17

runtime/ftplugin/lf.vim

@@ -0,0 +1,22 @@
+" Vim filetype plugin file
+" Language: lf file manager configuration file (lfrc)
+" Maintainer: Andis Sprinkis <andis@sprinkis.com>
+" URL: https://github.com/andis-sprinkis/lf-vim
+" Last Change: 6 Apr 2025
+
+if exists("b:did_ftplugin") | finish | endif
+
+let b:did_ftplugin = 1
+
+let s:cpo = &cpo
+set cpo&vim
+
+let b:undo_ftplugin = "setlocal comments< commentstring< formatoptions<"
+
+setlocal comments=:#
+setlocal commentstring=#\ %s
+
+setlocal formatoptions-=t formatoptions+=rol
+
+let &cpo = s:cpo
+unlet s:cpo

runtime/syntax/lf.vim

@@ -3,15 +3,13 @@
 " Maintainer: Andis Sprinkis <andis@sprinkis.com>
 " Former Maintainer: Cameron Wright
 " URL: https://github.com/andis-sprinkis/lf-vim
-" Last Change: 28 March 2025
+" Last Change: 5 Apr 2025
-" 29 Mar 2025 by Vim Project (save and restore 'cpo' setting)
 "
 " The shell syntax highlighting is configurable. See $VIMRUNTIME/doc/syntax.txt
 " lf version: 34
 
-if exists("b:current_syntax")
+if exists("b:current_syntax") | finish | endif
-    finish
+
-endif
 let s:cpo = &cpo
 set cpo&vim
 
@@ -23,11 +21,7 @@ syn match    lfComment        '#.*$'
 
 "{{{ String Matching
 syn match lfString "'.*'"
-syn match    lfString         '".*"' contains=lfVar,lfSpecial
+syn match lfString '".*"' contains=lfSpecial
-"}}}
-
-"{{{ Match lf Variables
-syn match    lfVar            '\$f\|\$fx\|\$fs\|\$id'
 "}}}
 
 "{{{ Keywords
@@ -45,6 +39,7 @@ syn keyword  lfOptions
   \ cleaner
   \ clear
   \ clearmaps
+  \ cmaps
   \ cmd-capitalize-word
   \ cmd-complete
   \ cmd-delete
@@ -73,6 +68,7 @@ syn keyword  lfOptions
   \ cmd-word
   \ cmd-word-back
   \ cmd-yank
+  \ cmds
   \ copy
   \ copyfmt
   \ cursoractivefmt
@@ -86,6 +82,7 @@ syn keyword  lfOptions
   \ dirfirst
   \ dironly
   \ dirpreviews
+  \ doc
   \ down
   \ draw
   \ drawbox
@@ -127,6 +124,7 @@ syn keyword  lfOptions
   \ load
   \ locale
   \ low
+  \ maps
   \ mark-load
   \ mark-remove
   \ mark-save
@@ -207,38 +205,33 @@ syn keyword  lfOptions
 "}}}
 
 "{{{ Special Matching
-syn match    lfSpecial        '<.*>\|\\.'
+syn match lfSpecial '\v\<[^>]+\>'
+syn match lfSpecial '\v\\(["\\abfnrtv]|\o+)'
 "}}}
 
 "{{{ Shell Script Matching for cmd
 let s:shell_syntax = get(g:, 'lf_shell_syntax', "syntax/sh.vim")
 let s:shell_syntax = get(b:, 'lf_shell_syntax', s:shell_syntax)
+
 unlet b:current_syntax
 exe 'syn include @Shell '.s:shell_syntax
 let b:current_syntax = "lf"
-syn region   lfIgnore         start=".{{\n" end="^}}"
+
-    \ keepend contains=lfExternalShell,lfExternalPatch
+syn region lfCommand matchgroup=lfCommandMarker start=' \zs:\ze' end='$' keepend transparent
-syn match    lfShell          '\$[a-zA-Z].*$
+syn region lfCommand matchgroup=lfCommandMarker start=' \zs:{{\ze' end='}}' keepend transparent
-    \\|:[a-zA-Z].*$
+syn region lfShell matchgroup=lfShellMarker start=' \zs[$!%&]\ze' end='$' keepend contains=@Shell
-    \\|%[a-zA-Z].*$
+syn region lfShell matchgroup=lfShellMarker start=' \zs[$!%&]{{\ze' end='}}' keepend contains=@Shell
-    \\|![a-zA-Z].*$
-    \\|&[a-zA-Z].*$'
-    \ transparent contains=@Shell,lfExternalPatch
-syn match    lfExternalShell  "^.*$" transparent contained contains=@Shell
-syn match    lfExternalPatch  "^\s*cmd\ .*\ .{{$\|^}}$" contained
 "}}}
 
 "{{{ Link Highlighting
 hi def link lfComment       Comment
-hi def link  lfVar            Type
+hi def link lfSpecial       SpecialChar
-hi def link  lfSpecial        Special
 hi def link lfString        String
 hi def link lfKeyword       Statement
 hi def link lfOptions       Constant
-hi def link  lfConstant       Constant
+hi def link lfCommandMarker Special
-hi def link  lfExternalShell  Normal
+hi def link lfShellMarker   Special
-hi def link  lfExternalPatch  Special
-hi def link  lfIgnore         Special
 "}}}
+
 let &cpo = s:cpo
 unlet s:cpo