Use ui_path() as it was designed to be used (r-lib#1861)

* Use ui_path() as it was designed to be used

Closes r-lib#1859

* Add a test

R/write.R

@@ -60,7 +60,7 @@ write_union <- function(path, lines, quiet = FALSE) {
   }
 
   if (!quiet) {
-    ui_done("Adding {ui_value(new)} to {ui_path(proj_rel_path(path))}")
+    ui_done("Adding {ui_value(new)} to {ui_path(path)}")
   }
 
   all <- c(existing_lines, new)

tests/testthat/_snaps/write.md

@@ -0,0 +1,7 @@
+# write_union() messaging is correct with weird working directory
+
+    Code
+      write_union(proj_path("somefile"), letters[4:6])
+    Message
+      v Adding 'd', 'e', 'f' to 'somefile'
+

tests/testthat/test-write.R

@@ -240,3 +240,15 @@ test_that("write_over() works for a file in a project that is not active", {
   )
   expect_false(proj_active())
 })
+
+test_that("write_union() messaging is correct with weird working directory", {
+  create_local_project()
+  withr::local_options(usethis.quiet = FALSE)
+
+  use_directory("aaa/bbb")
+  setwd("aaa/bbb")
+
+  expect_snapshot(
+    write_union(proj_path("somefile"), letters[4:6])
+  )
+})