[R] [ci] remove dependency on {devtools} (#8563)

R-package/DESCRIPTION

@@ -65,4 +65,5 @@ Imports:
     data.table (>= 1.9.6),
     jsonlite (>= 1.0),
 RoxygenNote: 7.2.2
+Encoding: UTF-8
 SystemRequirements: GNU make, C++14

R-package/demo/caret_wrapper.R

@@ -1,5 +1,4 @@
 # install development version of caret library that contains xgboost models
-devtools::install_github("topepo/caret/pkg/caret")
 require(caret)
 require(xgboost)
 require(data.table)

R-package/tests/helper_scripts/install_deps.R

@@ -3,7 +3,9 @@
 ## inconsistent is found.
 pkgs <- c(
   ## CI
-  "devtools",
+  "caret",
+  "pkgbuild",
+  "roxygen2",
   "XML",
   "cplm",
   "e1071",

demo/kaggle-otto/README.MD

@@ -16,7 +16,7 @@ The parameter `nthread` controls the number of cores to run on, please set it to
 To install the R-package of xgboost, please run
 
 ```r
-devtools::install_github('tqchen/xgboost',subdir='R-package')
+install.packages("xgboost", repos = "https://cran.r-project.org")
 ```
 
 Windows users may need to install [RTools](http://cran.r-project.org/bin/windows/Rtools/) first.

doc/build.rst

@@ -313,7 +313,7 @@ Installing the development version (Linux / Mac OSX)
 Make sure you have installed git and a recent C++ compiler supporting C++11 (See above
 sections for requirements of building C++ core).
 
-Due to the use of git-submodules, ``devtools::install_github`` can no longer be used to
+Due to the use of git-submodules, ``remotes::install_github()`` cannot be used to
 install the latest version of R package. Thus, one has to run git to check out the code
 first, see :ref:`get_source` on how to initialize the git repository for XGBoost. The
 simplest way to install the R package after obtaining the source code is:

tests/ci_build/test_r_package.py

@@ -152,15 +152,16 @@ def check_rmarkdown() -> None:
     assert system() != "Windows", "Document test doesn't support Windows."
     env = os.environ.copy()
     env.update({"MAKEFLAGS": f"-j{os.cpu_count()}"})
-    print("Checking R document with devtools.")
+    print("Checking R documentation.")
     bin_dir = os.path.dirname(R)
     rscript = os.path.join(bin_dir, "Rscript")
-    subprocess.check_call([rscript, "-e", "devtools::document()"], env=env)
+    subprocess.check_call([rscript, "-e", "roxygen2::roxygenize()"], env=env)
     output = subprocess.run(["git", "diff", "--name-only"], capture_output=True)
     if len(output.stdout.decode("utf-8").strip()) != 0:
         output = subprocess.run(["git", "diff"], capture_output=True)
         raise ValueError(
-            "Please run `devtools::document()`. Diff:\n", output.stdout.decode("utf-8")
+            "Please run `roxygen2::roxygenize()`. Diff:\n",
+            output.stdout.decode("utf-8"),
         )