[Rd] potential file.copy() or documentation bug when copy.date = TRUE

[Gábor Csárdi]

This is a recent R-devel. file.copy() is not vectorized if multiple
destinations succeed:

cat("foo1\n", file = "foo1")
cat("foo2\n", file = "foo2")
unlink(c("copy1", "copy2"), recursive = TRUE)

file.copy(c("foo1", "foo2"), c("copy1", "copy2"), copy.date = TRUE)

#> Error in Sys.setFileTime(to[okay], fi$mtime) : invalid 'path' argument

# But the files were still copied:
file.exists(c("copy1", "copy2"))
#> [1] TRUE TRUE

file.copy(c("foo1", "foo2"), c("copy1", "copy2"))
#> [1] FALSE FALSE

file.copy(c("foo1", "foo2"), c("copy1", "copy2"), copy.date = TRUE)
#> [1] FALSE FALSE

file.copy(c("foo1", "foo2"), c("copy1", "copy2"), copy.date = TRUE,
overwrite = TRUE)
#> Error in Sys.setFileTime(to[okay], fi$mtime) : invalid 'path' argument