From 015102e91e978a0bb42a14461c132a85e8f7e1ea Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Sat, 16 Jul 2016 18:24:56 +0200
Subject: patch 7.4.2050 Problem:    When using ":vimgrep" may end up with
 duplicate buffers. Solution:   When adding an error list entry pass the
 buffer number if possible.

---
 src/quickfix.c                | 13 ++++++++++---
 src/testdir/test_quickfix.vim | 15 +++++++++++++++
 src/version.c                 |  2 ++
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/quickfix.c b/src/quickfix.c
index 1fb47a009..1145896e1 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -1581,7 +1581,7 @@ static char_u *qf_last_bufname = NULL;
 static bufref_T  qf_last_bufref = {NULL, 0};
 
 /*
- * Get buffer number for file "dir.name".
+ * Get buffer number for file "directory.fname".
  * Also sets the b_has_qf_entry flag.
  */
     static int
@@ -4109,11 +4109,13 @@ ex_vimgrep(exarg_T *eap)
 		while (vim_regexec_multi(&regmatch, curwin, buf, lnum,
 							       col, NULL) > 0)
 		{
-		    ;
+		    /* Pass the buffer number so that it gets used even for a
+		     * dummy buffer, unless duplicate_name is set, then the
+		     * buffer will be wiped out below. */
 		    if (qf_add_entry(qi,
 				NULL,       /* dir */
 				fname,
-				0,
+				duplicate_name ? 0 : buf->b_fnum,
 				ml_get_buf(buf,
 				     regmatch.startpos[0].lnum + lnum, FALSE),
 				regmatch.startpos[0].lnum + lnum,
@@ -4177,12 +4179,17 @@ ex_vimgrep(exarg_T *eap)
 		    else if (buf != first_match_buf || (flags & VGR_NOJUMP))
 		    {
 			unload_dummy_buffer(buf, dirname_start);
+			/* Keeping the buffer, remove the dummy flag. */
+			buf->b_flags &= ~BF_DUMMY;
 			buf = NULL;
 		    }
 		}
 
 		if (buf != NULL)
 		{
+		    /* Keeping the buffer, remove the dummy flag. */
+		    buf->b_flags &= ~BF_DUMMY;
+
 		    /* If the buffer is still loaded we need to use the
 		     * directory we jumped to below. */
 		    if (buf == first_match_buf
diff --git a/src/testdir/test_quickfix.vim b/src/testdir/test_quickfix.vim
index 9fbef15f8..a4f8b3595 100644
--- a/src/testdir/test_quickfix.vim
+++ b/src/testdir/test_quickfix.vim
@@ -1462,3 +1462,18 @@ func Test_history()
   call HistoryTest('c')
   call HistoryTest('l')
 endfunc
+
+func Test_duplicate_buf()
+  " make sure we can get the highest buffer number
+  edit DoesNotExist
+  edit DoesNotExist2
+  let last_buffer = bufnr("$")
+
+  " make sure only one buffer is created
+  call writefile(['this one', 'that one'], 'Xgrepthis')
+  vimgrep one Xgrepthis
+  vimgrep one Xgrepthis
+  call assert_equal(last_buffer + 1, bufnr("$"))
+
+  call delete('Xgrepthis')
+endfunc
diff --git a/src/version.c b/src/version.c
index f0df84806..f4d90907f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2050,
 /**/
     2049,
 /**/
-- 
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