adding showdiff for symlink for #156

dotdrop/installer.py

@@ -216,6 +216,10 @@ class Installer:
             if self.dry:
                 self.log.dry('would remove {} and link to {}'.format(dst, src))
                 return True, None
+            if self.showdiff:
+                with open(src, 'rb') as f:
+                    content = f.read()
+                self._diff_before_write(src, dst, content)
             msg = 'Remove "{}" for link creation?'.format(dst)
             if self.safe and not self.log.ask(msg):
                 err = 'ignoring "{}", link was not created'.format(dst)