[PATCH] diff.c: flush stdout before printing rename warnings

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

The diff output is buffered in a FILE object and could still be
partially buffered when we print these warnings (directly to fd 2).
The output is messed up like this

 worktree.c                                   |   138 +-
 worktree.h        warning: inexact rename detection was skipped due to too many files.
                           |    12 +-
 wrapper.c                                    |    83 +-

It gets worse if the warning is printed after color codes for the graph
part are already printed. You'll get a warning in green or red.

Flush stdout first, so we can get something like this instead:

 xdiff/xutils.c                               |    42 +-
 xdiff/xutils.h                               |     4 +-
 1033 files changed, 150824 insertions(+), 69395 deletions(-)
warning: inexact rename detection was skipped due to too many files.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 diff.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/diff.c b/diff.c
index fb22b19f09..5545c25640 100644
--- a/diff.c
+++ b/diff.c
@@ -5454,6 +5454,7 @@ N_("you may want to set your %s variable to at least "
 
 void diff_warn_rename_limit(const char *varname, int needed, int degraded_cc)
 {
+	fflush(stdout);
 	if (degraded_cc)
 		warning(_(degrade_cc_to_c_warning));
 	else if (needed)
-- 
2.15.1.600.g899a5f85c6