[LyX/master] Simplify use of Buffer::getBackupName().

[Richard Heck]

commit 9efa43d2be7dcff0c1152b6f6a45801cfdd6d70e
Author: Richard Heck <rgh...@lyx.org>
Date:   Fri Nov 13 17:12:52 2015 -0500

    Simplify use of Buffer::getBackupName().
    
    Previous versions of this code used the string in a different way,
    but now it is sufficient just to return a FileName.

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index f907d6c..b1807ed 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -1306,7 +1306,7 @@ Buffer::ReadStatus Buffer::convertLyXFormat(FileName 
const & fn,
 }
 
 
-string Buffer::getBackupName() const {
+FileName Buffer::getBackupName() const {
        FileName const & fn = fileName();
        string const fname = fn.onlyFileNameWithoutExt();
        string const fext  = fn.extension();
@@ -1337,7 +1337,7 @@ string Buffer::getBackupName() const {
                backup.set(addName(fpath, addExtension(newbackname, fext)));
                v++;
        }
-       return v < 100 ? backup.absFileName() : "";
+       return v < 100 ? backup : FileName();
 }
 
 
@@ -1402,11 +1402,8 @@ bool Buffer::save() const
 
        FileName backupName;
        if (lyxrc.make_backup || d->need_format_backup) {
-               if (d->need_format_backup) {
-                       string backup_name = getBackupName();
-                       if (!backup_name.empty())
-                               backupName.set(backup_name);
-               }
+               if (d->need_format_backup)
+                       backupName = getBackupName();
 
                // If we for some reason failed to find a backup name in case of
                // a format change, this will still set one. It's the best we 
can
diff --git a/src/Buffer.h b/src/Buffer.h
index 7dd9365..7450790 100644
--- a/src/Buffer.h
+++ b/src/Buffer.h
@@ -268,7 +268,7 @@ private:
        ReadStatus convertLyXFormat(support::FileName const & fn,
                support::FileName & tmpfile, int from_format);
        /// get appropriate name for backing up files from older versions
-       std::string getBackupName() const;
+       support::FileName getBackupName() const;
        //@}
 
 public: