patch 8.2.4238: *.tf file could be fileytpe "tf" or "terraform"

Problem:    *.tf file could be fileytpe "tf" or "terraform".
Solution:   Detect the type from the file contents. (closes #9642)

runtime/autoload/dist/ft.vim

@@ -862,6 +862,21 @@ func dist#ft#FTfoam()
     endwhile
 endfunc
 
+" Determine if a *.tf file is TF mud client or terraform
+func dist#ft#FTtf()
+  let numberOfLines = line('$')
+  for i in range(1, numberOfLines)
+    let currentLine = trim(getline(i))
+    let firstCharacter = currentLine[0]
+    if firstCharacter !=? ";" && firstCharacter !=? "/" && firstCharacter !=? ""
+      setf terraform
+      return
+    endif
+  endfor
+  setf tf
+endfunc
+
+
 " Restore 'cpoptions'
 let &cpo = s:cpo_save
 unlet s:cpo_save

runtime/filetype.vim

@@ -1946,10 +1946,13 @@ au BufNewFile,BufRead texmf.cnf			setf texmf
 au BufNewFile,BufRead .tidyrc,tidyrc,tidy.conf	setf tidy
 
 " TF mud client
-au BufNewFile,BufRead *.tf,.tfrc,tfrc		setf tf
+au BufNewFile,BufRead .tfrc,tfrc		setf tf
+
+" TF mud client or terraform
+au BufNewFile,BufRead *.tf			call dist#ft#FTtf()
 
 " TLA+
-au BufRead,BufNewFile *.tla			setf tla
+au BufNewFile,BufRead *.tla			setf tla
 
 " tmux configuration
 au BufNewFile,BufRead {.,}tmux*.conf		setf tmux
@@ -1958,7 +1961,7 @@ au BufNewFile,BufRead {.,}tmux*.conf		setf tmux
 au BufNewFile,BufRead *.toml			setf toml
 
 " TPP - Text Presentation Program
-au BufNewFile,BufReadPost *.tpp			setf tpp
+au BufNewFile,BufRead *.tpp			setf tpp
 
 " Treetop
 au BufRead,BufNewFile *.treetop			setf treetop

src/testdir/test_filetype.vim

@@ -771,6 +771,24 @@ func Test_hook_file()
   filetype off
 endfunc
 
+func Test_tf_file()
+  filetype on
+
+  call writefile([';;; TF MUD client is super duper cool'], 'Xfile.tf')
+  split Xfile.tf
+  call assert_equal('tf', &filetype)
+  bwipe!
+
+  call writefile(['provider "azurerm" {'], 'Xfile.tf')
+  split Xfile.tf
+  call assert_equal('terraform', &filetype)
+  bwipe!
+
+  call delete('Xfile.tf')
+  filetype off
+endfunc
+
+
 func Test_ts_file()
   filetype on
 

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4238,
 /**/
     4237,
 /**/