patch 9.1.0948: Missing cmdline completion for :pbuffer

Problem:  Missing cmdline completion for :pbuffer.
Solution: Add cmdline completion for :pbuffer like :buffer.
          (zeertzjq)

fixes: #16250
closes: #16251

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index 7e53114..3ceb6c7 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -2332,6 +2332,7 @@
 	    // FALLTHROUGH
 	case CMD_buffer:
 	case CMD_sbuffer:
+	case CMD_pbuffer:
 	case CMD_checktime:
 	    xp->xp_context = EXPAND_BUFFERS;
 	    xp->xp_pattern = arg;
diff --git a/src/testdir/test_preview.vim b/src/testdir/test_preview.vim
index 0df1a90..7c7883a 100644
--- a/src/testdir/test_preview.vim
+++ b/src/testdir/test_preview.vim
@@ -47,12 +47,23 @@
   edit Xpreview.c
   const buf_num = bufnr('%')
   enew
+
+  call feedkeys(":pbuffer Xpre\<C-A>\<C-B>\"\<CR>", 'xt')
+  call assert_equal("\"pbuffer Xpreview.c", @:)
+
   call assert_equal(1, winnr('$'))
   exe 'pbuffer ' .  buf_num
   call assert_equal(2, winnr('$'))
   call assert_equal(0, &previewwindow)
 
   call s:goto_preview_and_close()
+
+  call assert_equal(1, winnr('$'))
+  pbuffer Xpreview.c
+  call assert_equal(2, winnr('$'))
+  call assert_equal(0, &previewwindow)
+
+  call s:goto_preview_and_close()
 endfunc
 
 func Test_window_preview_terminal()
diff --git a/src/version.c b/src/version.c
index f026617..00088ff 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    948,
+/**/
     947,
 /**/
     946,