patch 8.2.0064: diffmode completion doesn't use per-window setting

Problem:    Diffmode completion doesn't use per-window setting.
Solution:   Check if a window is in diff mode. (Dominique Pell, closes #5419)

src/buffer.c

@@ -2661,6 +2661,11 @@ ExpandBufnames(
     *num_file = 0;		    // return values in case of FAIL
     *file = NULL;
 
+#ifdef FEAT_DIFF
+    if ((options & BUF_DIFF_FILTER) && !curwin->w_p_diff)
+	return FAIL;
+#endif
+
     // Make a copy of "pat" and change "^" to "\(^\|[\/]\)".
     if (*pat == '^')
     {
@@ -2706,8 +2711,7 @@ ExpandBufnames(
 		if (options & BUF_DIFF_FILTER)
 		    // Skip buffers not suitable for
 		    // :diffget or :diffput completion.
-		    if (buf == curbuf
+		    if (buf == curbuf || !diff_mode_buf(buf))
-			    || !diff_mode_buf(curbuf) || !diff_mode_buf(buf))
 			continue;
 #endif
 

src/testdir/test_diffmode.vim

@@ -242,43 +242,60 @@ func Test_diffput_two()
   bwipe! b
 endfunc
 
-func Test_diffget_diffput_completion()
-  new Xdiff1 | diffthis
-  new Xdiff2 | diffthis
-  new Xdiff3 | diffthis
-  new Xdiff4
-
 " :diffput and :diffget completes names of buffers which
 " are in diff mode and which are different then current buffer.
-  b Xdiff1
+" No completion when the current window is not in diff mode.
-  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+func Test_diffget_diffput_completion()
-  call assert_equal('"diffput Xdiff2 Xdiff3', @:)
+  e            Xdiff1 | diffthis
-  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
+  botright new Xdiff2
-  call assert_equal('"diffget Xdiff2 Xdiff3', @:)
+  botright new Xdiff3 | split | diffthis
-  call assert_equal(['Xdiff2', 'Xdiff3'], getcompletion('', 'diff_buffer'))
+  botright new Xdiff4 | diffthis
 
-  b Xdiff2
+  wincmd t
+  call assert_equal('Xdiff1', bufname('%'))
   call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
-  call assert_equal('"diffput Xdiff1 Xdiff3', @:)
+  call assert_equal('"diffput Xdiff3 Xdiff4', @:)
   call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
-  call assert_equal('"diffget Xdiff1 Xdiff3', @:)
+  call assert_equal('"diffget Xdiff3 Xdiff4', @:)
-  call assert_equal(['Xdiff1', 'Xdiff3'], getcompletion('', 'diff_buffer'))
+  call assert_equal(['Xdiff3', 'Xdiff4'], getcompletion('', 'diff_buffer'))
 
-  b Xdiff3
+  " Xdiff2 is not in diff mode, so no completion for :diffput, :diffget
-  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+  wincmd j
-  call assert_equal('"diffput Xdiff1 Xdiff2', @:)
+  call assert_equal('Xdiff2', bufname('%'))
-  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
-  call assert_equal('"diffget Xdiff1 Xdiff2', @:)
-  call assert_equal(['Xdiff1', 'Xdiff2'], getcompletion('', 'diff_buffer'))
-
-  " No completion when in Xdiff4, it's not in diff mode.
-  b Xdiff4
   call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
   call assert_equal('"diffput ', @:)
   call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
   call assert_equal('"diffget ', @:)
   call assert_equal([], getcompletion('', 'diff_buffer'))
 
+  " Xdiff3 is split in 2 windows, only the top one is in diff mode.
+  " So completion of :diffput :diffget only happens in the top window.
+  wincmd j
+  call assert_equal('Xdiff3', bufname('%'))
+  call assert_equal(1, &diff)
+  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffput Xdiff1 Xdiff4', @:)
+  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffget Xdiff1 Xdiff4', @:)
+  call assert_equal(['Xdiff1', 'Xdiff4'], getcompletion('', 'diff_buffer'))
+
+  wincmd j
+  call assert_equal('Xdiff3', bufname('%'))
+  call assert_equal(0, &diff)
+  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffput ', @:)
+  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffget ', @:)
+  call assert_equal([], getcompletion('', 'diff_buffer'))
+
+  wincmd j
+  call assert_equal('Xdiff4', bufname('%'))
+  call feedkeys(":diffput \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffput Xdiff1 Xdiff3', @:)
+  call feedkeys(":diffget \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"diffget Xdiff1 Xdiff3', @:)
+  call assert_equal(['Xdiff1', 'Xdiff3'], getcompletion('', 'diff_buffer'))
+
   %bwipe
 endfunc
 

src/version.c

@@ -742,6 +742,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    64,
 /**/
     63,
 /**/