patch 9.1.0616: filetype: Make syntax highlighting off for MS Makefiles

Problem:  filetype: Make syntax highlighting off for MS Makefiles
Solution: Try to detect MS Makefiles and adjust syntax rules to it.
          (Ken Takata)

Highlighting of variable expansion in Microsoft Makefile can be broken.
E.g.:
https://github.com/vim/vim/blob/2979cfc2627d76a9c09cad46a1647dcd4aa73f5f/src/Make_mvc.mak#L1331

Don't use backslash as escape characters if `make_microsoft` is set.
Also fix that `make_no_comments` was not considered if `make_microsoft`
was set.

Also add description for `make_microsoft` and `make_no_comments` to the
documentation and include a very simple filetype test

closes: #15341

Signed-off-by: Christian Brabandt <cb@256bit.org>
Signed-off-by: Ken Takata <kentkt@csc.jp>
diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index be299ef..e53cdac 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -532,6 +532,25 @@
   endif
 enddef
 
+export def FTmake()
+  # Check if it is a Microsoft Makefile
+  unlet! b:make_microsoft
+  var n = 1
+  while n < 1000 && n <= line('$')
+    var line = getline(n)
+    if line =~? '^\s*!\s*\(ifn\=\(def\)\=\|include\|message\|error\)\>'
+      b:make_microsoft = 1
+      break
+    elseif line =~ '^ *ifn\=\(eq\|def\)\>' || line =~ '^ *[-s]\=include\s'
+      break
+    elseif line =~ '^ *\w\+\s*[!?:+]='
+      break
+    endif
+    n += 1
+  endwhile
+  setf make
+enddef
+
 export def FTmms()
   var n = 1
   while n < 20
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index f843082..2f8d950 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.1.  Last change: 2024 Jul 23
+*syntax.txt*	For Vim version 9.1.  Last change: 2024 Jul 25
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2278,7 +2278,7 @@
 displayed line.  If you have a slow machine, and generally deal with emails
 with short headers, you can change this to a smaller value: >
 
-    :let mail_minlines = 30
+	:let mail_minlines = 30
 
 
 MAKE						*make.vim* *ft-make-syntax*
@@ -2289,6 +2289,16 @@
 
 	:let make_no_commands = 1
 
+Comments are also highlighted by default.  You can turn this off by using: >
+
+	:let make_no_comments = 1
+
+Microsoft Makefile handles variable expansion and comments differently
+(backslashes are not used for escape).  If you see any wrong highlights
+because of this, you can try this: >
+
+	:let make_microsoft = 1
+
 
 MAPLE						*maple.vim* *ft-maple-syntax*
 
diff --git a/runtime/filetype.vim b/runtime/filetype.vim
index b589a0b..d028265 100644
--- a/runtime/filetype.vim
+++ b/runtime/filetype.vim
@@ -1387,7 +1387,7 @@
 au BufNewFile,BufRead .mailcap,mailcap		setf mailcap
 
 " Makefile
-au BufNewFile,BufRead *[mM]akefile,*.mk,*.mak	setf make
+au BufNewFile,BufRead *[mM]akefile,*.mk,*.mak	call dist#ft#FTmake()
 au BufNewFile,BufRead Kbuild			setf make
 
 " MakeIndex
diff --git a/runtime/syntax/make.vim b/runtime/syntax/make.vim
index b457304..d3ddf78 100644
--- a/runtime/syntax/make.vim
+++ b/runtime/syntax/make.vim
@@ -28,8 +28,13 @@
 syn case match
 
 " identifiers
-syn region makeIdent	start="\$(" skip="\\)\|\\\\" end=")" contains=makeStatement,makeIdent
-syn region makeIdent	start="\${" skip="\\}\|\\\\" end="}" contains=makeStatement,makeIdent
+if exists("b:make_microsoft") || exists("make_microsoft")
+  syn region makeIdent	start="\$(" end=")" contains=makeStatement,makeIdent
+  syn region makeIdent	start="\${" end="}" contains=makeStatement,makeIdent
+else
+  syn region makeIdent	start="\$(" skip="\\)\|\\\\" end=")" contains=makeStatement,makeIdent
+  syn region makeIdent	start="\${" skip="\\}\|\\\\" end="}" contains=makeStatement,makeIdent
+endif
 syn match makeIdent	"\$\$\w*"
 syn match makeIdent	"\$[^({]"
 syn match makeIdent	"^ *[^:#= \t]*\s*[:+?!*]="me=e-2
@@ -78,11 +83,13 @@
 syn match makeStatement contained "(\(abspath\|addprefix\|addsuffix\|and\|basename\|call\|dir\|error\|eval\|file\|filter-out\|filter\|findstring\|firstword\|flavor\|foreach\|guile\|if\|info\|join\|lastword\|notdir\|or\|origin\|patsubst\|realpath\|shell\|sort\|strip\|subst\|suffix\|value\|warning\|wildcard\|word\|wordlist\|words\)\>"ms=s+1
 
 " Comment
-if exists("make_microsoft")
-   syn match  makeComment "#.*" contains=@Spell,makeTodo
-elseif !exists("make_no_comments")
-   syn region  makeComment	start="#" end="^$" end="[^\\]$" keepend contains=@Spell,makeTodo
-   syn match   makeComment	"#$" contains=@Spell
+if !exists("make_no_comments")
+  if exists("b:make_microsoft") || exists("make_microsoft")
+    syn match   makeComment	"#.*" contains=@Spell,makeTodo
+  else
+    syn region  makeComment	start="#" end="^$" end="[^\\]$" keepend contains=@Spell,makeTodo
+    syn match   makeComment	"#$" contains=@Spell
+  endif
 endif
 syn keyword makeTodo TODO FIXME XXX contained