Add check.names = FALSE to merge() in Ops.xts()

The check.names functionality was added to merge.xts() in commit
81df3f0. Setting it to FALSE in
Ops.xts() makes it consistent with Ops.zoo.

Fixes #114.

R/Ops.xts.R

@@ -36,8 +36,8 @@ function(e1, e2)
     .Class <- "matrix"
     NextMethod(.Generic)
     } else {
-      tmp.e1 <- merge.xts(e1, e2, all=FALSE, retclass=FALSE, retside=c(TRUE,FALSE))
-      e2 <- merge.xts(e2, e1, all=FALSE, retclass=FALSE, retside=c(TRUE,FALSE))
+      tmp.e1 <- merge.xts(e1, e2, all=FALSE, retclass=FALSE, retside=c(TRUE,FALSE), check.names=FALSE)
+      e2 <- merge.xts(e2, e1, all=FALSE, retclass=FALSE, retside=c(TRUE,FALSE), check.names=FALSE)
       e1 <- tmp.e1
       .Class <- "matrix"
       NextMethod(.Generic)

inst/unitTests/runit.Ops.R

@@ -510,3 +510,12 @@ test.tzone_after_rel_op <- function() {
   checkIdentical(tzone(ts2 == 0), tstz)
   checkIdentical(tzone(ts2 != 0), tstz)
 }
+
+test.Ops.xts_does_not_change_column_names <- function() {
+  x <- .xts(1:3, 1:3, dimnames = list(NULL, c("-1")))
+  z <- as.zoo(x)
+  checkEquals(names(x + x[-1,]), names(z + z[-1,]),
+              "Ops.xts() doesn't change column names when merge() is called")
+  checkEquals(names(x + x), names(z + z),
+              "Ops.xts() doesn't change column names when indexes are equal")
+}