fix(filetype): make vim.filetype.match() work with contents only (#22181)

Co-authored-by: Gregory Anders <greg@gpanders.com>

runtime/lua/vim/filetype.lua

@@ -2449,6 +2449,7 @@ local function match_pattern(name, path, tail, pat)
       return false
     end
   end
+
   -- If the pattern contains a / match against the full path, otherwise just the tail
   local fullpat = '^' .. pat .. '$'
   local matches
@@ -2526,11 +2527,10 @@ function M.match(args)
     name = api.nvim_buf_get_name(bufnr)
   end
 
+  local ft, on_detect
+
   if name then
     name = normalize_path(name)
-  end
-
-  local ft, on_detect
 
     -- First check for the simple case where the full path exists as a key
     local path = vim.fn.fnamemodify(name, ':p')
@@ -2587,6 +2587,7 @@ function M.match(args)
         end
       end
     end
+  end
 
   -- Finally, check file contents
   if contents or bufnr then

test/functional/lua/filetype_spec.lua

@@ -94,6 +94,14 @@ describe('vim.filetype', function()
       return vim.filetype.match({ buf = 0 })
     ]])
   end)
+
+  it('works with contents #22180', function()
+    eq('sh', exec_lua [[
+      -- Needs to be set so detect#sh doesn't fail
+      vim.g.ft_ignore_pat = "\\.\\(Z\\|gz\\|bz2\\|zip\\|tgz\\)$"
+      return vim.filetype.match({ contents = { '#!/usr/bin/env bash' } })
+    ]])
+  end)
 end)
 
 describe('filetype.lua', function()