vim-patch:8.2.1775: MS-Windows: adding a long quickfix list is slow (#13019)

vim-patch:8.2.1775: MS-Windows: adding a long quickfix list is slow

Problem:    MS-Windows: adding a long quickfix list is slow.
Solution:   Shorten the buffer name only for the first entry. (Yegappan
            Lakshmanan, closes vim/vim#7039, closes vim/vim#7033)
8ec92c9779

N/A patches for version.c:

vim-patch:8.1.2226: cannot use system copy/paste in non-xterm terminals

Problem:    Cannot use system copy/paste in non-xterm terminals.
Solution:   Instead of setting 'mouse' to "a" set it to "nvi" in defaults.vim.
5b418992cf

vim-patch:8.2.1772: cannot use CTRL-W <Down> to move out of a terminal window

Problem:    Cannot use CTRL-W <Down> to move out of a terminal window.
Solution:   Use special_to_buf() instead of mb_char2bytes(). (closes vim/vim#7045)
f43e7ac4ee

vim-patch:8.2.1774: GTK: hang when forced to exit

Problem:    GTK: hang when forced to exit.
Solution:   Do not clean up "mainwin" when really_exiting is set.
            (Zdenek Dohnal, closes vim/vim#7042)
32fbc4f247

vim-patch:8.2.1776: filetype.vim may be loaded twice

Problem:    Filetype.vim may be loaded twice.
Solution:   Do "syntax on" after "filetype on". (Adam Stankiewicz,
            closes vim/vim#7049)
17bb4d4607

src/nvim/quickfix.c

@@ -3752,7 +3752,7 @@ static void qf_update_buffer(qf_info_T *qi, qfline_T *old_last)
 
 // Add an error line to the quickfix buffer.
 static int qf_buf_add_line(buf_T *buf, linenr_T lnum, const qfline_T *qfp,
-                           char_u *dirname)
+                           char_u *dirname, bool first_bufline)
   FUNC_ATTR_NONNULL_ALL
 {
   int len;
@@ -3767,9 +3767,12 @@ static int qf_buf_add_line(buf_T *buf, linenr_T lnum, const qfline_T *qfp,
     if (qfp->qf_type == 1) {  // :helpgrep
       STRLCPY(IObuff, path_tail(errbuf->b_fname), IOSIZE - 1);
     } else {
-      // shorten the file name if not done already
+      // Shorten the file name if not done already.
-      if (errbuf->b_sfname == NULL
+      // For optimization, do this only for the first entry in a
-          || path_is_absolute(errbuf->b_sfname)) {
+      // buffer.
+      if (first_bufline
+          && (errbuf->b_sfname == NULL
+              || path_is_absolute(errbuf->b_sfname))) {
         if (*dirname == NUL) {
           os_dirname(dirname, MAXPATHL);
         }
@@ -3847,6 +3850,7 @@ static void qf_fill_buffer(qf_list_T *qfl, buf_T *buf, qfline_T *old_last)
   // Check if there is anything to display
   if (qfl != NULL) {
      char_u dirname[MAXPATHL];
+     int prev_bufnr = -1;
 
      *dirname = NUL;
 
@@ -3859,9 +3863,11 @@ static void qf_fill_buffer(qf_list_T *qfl, buf_T *buf, qfline_T *old_last)
       lnum = buf->b_ml.ml_line_count;
     }
     while (lnum < qfl->qf_count) {
-      if (qf_buf_add_line(buf, lnum, qfp, dirname) == FAIL) {
+      if (qf_buf_add_line(buf, lnum, qfp, dirname,
+                          prev_bufnr != qfp->qf_fnum) == FAIL) {
         break;
       }
+      prev_bufnr = qfp->qf_fnum;
       lnum++;
       qfp = qfp->qf_next;
       if (qfp == NULL) {

src/nvim/testdir/test_quickfix.vim

@@ -3473,6 +3473,18 @@ func Test_shorten_fname()
   " Displaying the quickfix list should simplify the file path
   silent! clist
   call assert_equal('test_quickfix.vim', bufname('test_quickfix.vim'))
+  " Add a few entries for the same file with different paths and check whether
+  " the buffer name is shortened
+  %bwipe
+  call setqflist([], 'f')
+  call setqflist([{'filename' : 'test_quickfix.vim', 'lnum' : 10},
+        \ {'filename' : '../testdir/test_quickfix.vim', 'lnum' : 20},
+        \ {'filename' : fname, 'lnum' : 30}], ' ')
+  copen
+  call assert_equal(['test_quickfix.vim|10| ',
+        \ 'test_quickfix.vim|20| ',
+        \ 'test_quickfix.vim|30| '], getline(1, '$'))
+  cclose
 endfunc
 
 " Quickfix title tests