Pass path to dir_ls in build_readme

Otherwise we assume the readme is always in the current working
directory.

Fixes #2344

Author: jimhester

NEWS.md

@@ -1,5 +1,7 @@
 # devtools (development version)
 
+* `build_readme()` now uses the `path` argument, as designed (#2344)
+
 * The RStudio addins now use `test_active_file()` and `test_coverage_active_file()` instead of the deprecated `test_file()` and `test_coverage_file()` (#2339)
 
 # devtools 2.4.0

R/build-readme.R

@@ -51,7 +51,7 @@ build_rmd <- function(files, path = ".", output_options = list(), ..., quiet = T
 build_readme <- function(path = ".", quiet = TRUE, ...) {
   pkg <- as.package(path)
 
-  readme_path <- path_abs(dir_ls(ignore.case = TRUE, regexp = "(inst/)?readme[.]rmd", recurse = 1, type = "file"))
+  readme_path <- path_abs(dir_ls(pkg$path, ignore.case = TRUE, regexp = "(inst/)?readme[.]rmd", recurse = 1, type = "file"))
 
   if (length(readme_path) == 0) {
     rlang::abort("Can't find a 'README.Rmd' or 'inst/README.Rmd' file.")