Do not give error exit status if pushing is just not enabled

dotfiles/gittum/bin/slurp

@@ -45,7 +45,10 @@ main() {
 
     git add .
     git commit -m "$(mkmsg)"
-    $want_push && git push
+    if $want_push;
+    then
+        git push
+    fi
 }
 
 main