[LyX/master] Fix bug #11490

[Enrico Forestieri]

commit c3b950483565ca53265a4105a4946585f8b59e24
Author: Enrico Forestieri <for...@lyx.org>
Date:   Tue Feb 19 19:51:11 2019 +0100

    Fix bug #11490
    
    Correctly add the branch name suffix when the stem
    of the filename contains a dot.
---
 src/Buffer.cpp |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index ff303a7..dc35734 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -812,10 +812,9 @@ FileName Buffer::Impl::exportFileName() const
        if (branch_suffix.empty())
                return filename;
 
-       string const name = filename.onlyFileNameWithoutExt()
-               + to_utf8(branch_suffix);
+       string const name = addExtension(filename.onlyFileNameWithoutExt()
+                       + to_utf8(branch_suffix), filename.extension());
        FileName res(filename.onlyPath().absFileName() + "/" + name);
-       res.changeExtension(filename.extension());
 
        return res;
 }