vim-patch:9.1.1342: Shebang filetype detection can be improved

Problem:  Shebang filetype detection can be improved
Solution: Improve detection logic (Eisuke Kawashima)

Vim does not correctly detect filetype from
  - `#!/usr/bin/env --split-string=awk -f`
  - `#!/usr/bin/env -S -i awk -f`
  - `#!/usr/bin/env -S VAR= awk -f`
So update the current detection logic to detect those cases.

closes: vim/vim#17199

f102f4c2e8

Co-authored-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com>

runtime/lua/vim/filetype/detect.lua

@@ -1959,11 +1959,10 @@ local function match_from_hashbang(contents, path, dispatch_extension)
   -- "#!/usr/bin/bash" to make matching easier.
   -- Recognize only a few {options} that are commonly used.
   if matchregex(first_line, [[^#!\s*\S*\<env\s]]) then
-    first_line = first_line:gsub('%S+=%S+', '')
-    first_line = first_line
-      :gsub('%-%-ignore%-environment', '', 1)
-      :gsub('%-%-split%-string', '', 1)
-      :gsub('%-[iS]', '', 1)
+    first_line = fn.substitute(first_line, [[\s\zs--split-string\(\s\|=\)]], '', '')
+    first_line = fn.substitute(first_line, [[\s\zs[A-Za-z0-9_]\+=\S*\ze\s]], '', 'g')
+    first_line =
+      fn.substitute(first_line, [[\s\zs\%(-[iS]\+\|--ignore-environment\)\ze\s]], '', 'g')
     first_line = fn.substitute(first_line, [[\<env\s\+]], '', '')
   end
 

test/old/testdir/test_filetype.vim

@@ -1068,10 +1068,10 @@ func s:GetScriptEnvChecks() abort
   return {
       \ 'perl': [['#!/usr/bin/env VAR=val perl']],
       \ 'scala': [['#!/usr/bin/env VAR=val VVAR=vval scala']],
-      \ 'awk': [['#!/usr/bin/env VAR=val -i awk']],
+      \ 'awk': [['#!/usr/bin/env --split-string=VAR= awk -vFS="," -f']],
       \ 'execline': [['#!/usr/bin/env execlineb']],
       \ 'scheme': [['#!/usr/bin/env VAR=val --ignore-environment scheme']],
-      \ 'python': [['#!/usr/bin/env VAR=val -S python -w -T']],
+      \ 'python': [['#!/usr/bin/env -S -i VAR=val python -B -u']],
       \ 'wml': [['#!/usr/bin/env VAR=val --split-string wml']],
       \ 'nix': [['#!/usr/bin/env nix-shell']],
       \ }