vim-patch:9.1.1304: filetype: some man files are not recognized

Problem:  filetype: some man files are not recognized
          (e.g. 1p (POSIX commands))
Solution: update the filetype detection pattern and detect more man
          files as nroff (Eisuke Kawashima)

- sections are revised referring to
    - debian-12:/etc/manpath.config
    - fedora-41:/etc/man_db.conf
- detection logic is improved
- detection test is implemented

closes: vim/vim#17117

babdb0554a

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

runtime/lua/vim/filetype.lua

@@ -696,7 +696,7 @@ local extension = {
   lex = 'lex',
   lxx = 'lex',
   ['l++'] = 'lex',
-  l = 'lex',
+  l = detect_seq('lex', detect.nroff),
   lhs = 'lhaskell',
   lidr = 'lidris2',
   ly = 'lilypond',
@@ -835,6 +835,7 @@ local extension = {
   nix = 'nix',
   norg = 'norg',
   nqc = 'nqc',
+  ['0'] = detect.nroff,
   ['1'] = detect.nroff,
   ['2'] = detect.nroff,
   ['3'] = detect.nroff,
@@ -844,6 +845,24 @@ local extension = {
   ['7'] = detect.nroff,
   ['8'] = detect.nroff,
   ['9'] = detect.nroff,
+  ['0p'] = detect.nroff,
+  ['1p'] = detect.nroff,
+  ['3p'] = detect.nroff,
+  ['1x'] = detect.nroff,
+  ['2x'] = detect.nroff,
+  ['3x'] = detect.nroff,
+  ['4x'] = detect.nroff,
+  ['5x'] = detect.nroff,
+  ['6x'] = detect.nroff,
+  ['7x'] = detect.nroff,
+  ['8x'] = detect.nroff,
+  ['3am'] = detect.nroff,
+  ['3perl'] = detect.nroff,
+  ['3pm'] = detect.nroff,
+  ['3posix'] = detect.nroff,
+  ['3type'] = detect.nroff,
+  n = detect.nroff,
+  o = detect.nroff,
   roff = 'nroff',
   tmac = 'nroff',
   man = 'nroff',
@@ -1390,7 +1409,7 @@ local extension = {
   pp = detect.pp,
   i = detect.i,
   w = detect.progress_cweb,
-  p = detect.progress_pascal,
+  p = detect_seq(detect.nroff, detect.progress_pascal),
   pro = detect_seq(detect.proto, 'idlang'),
   patch = detect.patch,
   r = detect.r,

runtime/lua/vim/filetype/detect.lua

@@ -1175,7 +1175,7 @@ end
 --- @type vim.filetype.mapfn
 function M.nroff(_, bufnr)
   for _, line in ipairs(getlines(bufnr, 1, 5)) do
-    if line:find('^%.') then
+    if line:find('^%.%S%S?') then
       return 'nroff'
     end
   end

test/old/testdir/test_filetype.vim

@@ -2918,6 +2918,20 @@ func Test_map_file()
   filetype off
 endfunc
 
+func Test_nroff_file()
+  filetype on
+
+  call writefile(['.TH vim 1 "YYYY Mth DD"'], 'Xfile.1', 'D')
+  split Xfile.1
+  call assert_equal('nroff', &filetype)
+  bwipe!
+
+  call writefile(['. /etc/profile'], 'Xfile.1', 'D')
+  split Xfile.1
+  call assert_notequal('nroff', &filetype)
+  bwipe!
+endfunc
+
 func Test_org_file()
   filetype on