add option to show diff before asking to overwrite

tests/helpers.py

@@ -80,6 +80,7 @@ def load_config(confpath, profile):
     opts['safe'] = True
     opts['installdiff'] = True
     opts['link'] = False
+    opts['showdiff'] = True
     opts['debug'] = True
     opts['dopts'] = ''
     opts['variables'] = {}

tests/test_install.py

@@ -174,6 +174,7 @@ exec bspwm
         conf, opts = load_config(confpath, profile)
         opts['safe'] = False
         opts['debug'] = True
+        opts['showdiff'] = True
         opts['variables'] = {}
         install(opts, conf)