patch 9.1.2027: filetype: bicep filetype used for 2 bicep file types

Problem:  filetype: bicep filetype used for 2 bicep file types
Solution: Detect *.bicepparam files as bicep-param filetype, include
          new bicep-params and bicep filetype plugin
          (Scott McKendry)

The bicep language server handles parameter files differently than
regular bicep files. Treating them the same at the editor level leads to
false positive diagnostics in the editor.

References:

Bicep Language Constants:
- https://github.com/Azure/bicep/blob/51392d32ca2c8b94b1bb7a255e78e1d559d12573/src/Bicep.Core/LanguageConstants.cs#L23
VS Code Extension definition:
- https://github.com/Azure/bicep/blob/51392d32ca2c8b94b1bb7a255e78e1d559d12573/src/vscode-bicep/package.json#L47

closes: #19026

Signed-off-by: Scott McKendry <me@scottmckendry.tech>
Signed-off-by: Christian Brabandt <cb@256bit.org>

.github/MAINTAINERS

@@ -127,6 +127,8 @@ runtime/ftplugin/asy.vim				@avidseeker
 runtime/ftplugin/autohotkey.vim				@telemachus
 runtime/ftplugin/awk.vim				@dkearns
 runtime/ftplugin/basic.vim				@dkearns
+runtime/ftplugin/bicep.vim				@scottmckendry
+runtime/ftplugin/bicep-params.vim				@scottmckendry
 runtime/ftplugin/brighterscript.vim			@ribru17
 runtime/ftplugin/brightscript.vim			@ribru17
 runtime/ftplugin/bst.vim				@tpope

runtime/autoload/dist/ft.vim

@@ -3,7 +3,7 @@ vim9script
 # Vim functions for file type detection
 #
 # Maintainer:		The Vim Project <https://github.com/vim/vim>
-# Last Change:		2025 Dec 26
+# Last Change:		2025 Dec 27
 # Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 # These functions are moved here from runtime/filetype.vim to make startup
@@ -1746,7 +1746,7 @@ const ft_from_ext = {
   "bst": "bst",
   # Bicep
   "bicep": "bicep",
-  "bicepparam": "bicep",
+  "bicepparam": "bicep-params",
   # BIND zone
   "zone": "bindzone",
   # Blank

runtime/ftplugin/bicep-params.vim

@@ -0,0 +1,3 @@
+" Placeholder for maximum compatibility. While bicepparam files are treated as distinct filetypes,
+" they are should share the same ftplugin settings as bicep files.
+runtime! ftplugin/bicep.vim

runtime/ftplugin/bicep.vim

@@ -0,0 +1,14 @@
+" Vim filetype plugin
+" Language:	Bicep
+" Maintainer:	Scott McKendry <me@scottmckendry.tech>
+" Last Change:	2025 Dec 27
+
+if exists('b:did_ftplugin')
+  finish
+endif
+let b:did_ftplugin = 1
+
+setlocal comments=s1:/*,mb:*,ex:*/,://
+setlocal commentstring=//\ %s
+
+let b:undo_ftplugin = "setlocal comments< commentstring<"

src/testdir/test_filetype.vim

@@ -140,7 +140,8 @@ def s:GetFilenameChecks(): dict<list<string>>
     bdf: ['file.bdf'],
     beancount: ['file.beancount'],
     bib: ['file.bib'],
-    bicep: ['file.bicep', 'file.bicepparam'],
+    bicep: ['file.bicep'],
+    bicep-params: ['file.bicepparam'],
     bindzone: ['named.root', '/bind/db.file', '/named/db.file', 'any/bind/db.file', 'any/named/db.file', 'foobar.zone'],
     bitbake: ['file.bb', 'file.bbappend', 'file.bbclass', 'build/conf/local.conf', 'meta/conf/layer.conf', 'build/conf/bbappend.conf', 'meta-layer/conf/distro/foo.conf',
       'project-spec/configs/zynqmp-generic-xczu7ev.conf'],

src/version.c

@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2027,
 /**/
     2026,
 /**/