Minor tweaks per #1519 (comment)

Author: koneill

NEWS.md

@@ -1,5 +1,9 @@
 # ggplot2 2.0.0.9000
 
+* `theme_update()` now uses the `+` operator instead of `%+replace%`, so that
+  unspecified values will no longer be `NULL`ed out. `theme_replace()`
+  preserves the old behaviour if desired.
+
 * `layer()` now accepts a function as the data argument. The function will be
   applied to the data passed to the `ggplot()` function and must return a
   data.frame (#1527).

R/theme.r

@@ -46,15 +46,12 @@
 #'  theme(legend.background = element_rect(fill = "white", colour = "white", size = 3))
 #'
 theme_update <- function(...) {
-  # Make a call to theme, then add to theme
   theme_set(theme_get() + theme(...))
 }
 
 #' @rdname theme_update
 #' @export
-
 theme_replace <- function(...) {
-  # Make a call to theme, then add to theme
   theme_set(theme_get() %+replace% theme(...))
 }