[docs] Make building the cpu-only docs build explicit (#13315)

The docs are usually built with a GPU, so this PR simplifies some logic
that was conflating several options to automatically choose the docker
image to run. Now the CPU image is only used if the `--cpu` flag is
passed, which makes `ci.py docs` work like CI by default for the main
docs.

.github/workflows/update_nightly_branch.yml

@@ -30,7 +30,7 @@ concurrency:
 
 jobs:
   update-nightly-branch:
-    if: github.repository == 'driazati/tvm'
+    if: github.repository == 'apache/tvm'
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2

tests/scripts/ci.py

@@ -232,6 +232,7 @@ def docker(
 
 def docs(
     tutorial_pattern: Optional[str] = None,
+    cpu: bool = False,
     full: bool = False,
     interactive: bool = False,
     skip_build: bool = False,
@@ -242,8 +243,9 @@ def docs(
     the Python docs without any tutorials.
 
     arguments:
-    full -- Build all language docs, not just Python (this will use the 'ci_gpu' Docker image)
-    tutorial-pattern -- Regex for which tutorials to execute when building docs (this will use the 'ci_gpu' Docker image)
+    full -- Build all language docs, not just Python (cannot be used with --cpu)
+    cpu -- Use the 'ci_cpu' Docker image (useful for building docs on a machine without a GPU)
+    tutorial-pattern -- Regex for which tutorials to execute when building docs (cannot be used with --cpu)
     skip_build -- skip build and setup scripts
     interactive -- start a shell after running build / test scripts
     docker-image -- manually specify the docker image to use
@@ -252,7 +254,7 @@ def docs(
 
     extra_setup = []
     image = "ci_gpu" if docker_image is None else docker_image
-    if not full and tutorial_pattern is None:
+    if cpu:
         # TODO: Change this to tlcpack/docs once that is uploaded
         image = "ci_cpu" if docker_image is None else docker_image
         build_dir = get_build_dir("cpu")
@@ -285,7 +287,7 @@ def docs(
         ]
 
         extra_setup = [
-            "python3 -m pip install --user " + " ".join(requirements),
+            "python3 -m pip install " + " ".join(requirements),
         ]
     else:
         check_gpu()
@@ -311,6 +313,13 @@ def docs(
         "TVM_LIBRARY_PATH": str(REPO_ROOT / build_dir),
     }
     docker(name=gen_name("docs"), image=image, scripts=scripts, env=env, interactive=interactive)
+    print_color(
+        col.GREEN,
+        "Done building the docs. You can view them by running "
+        "'python3 tests/scripts/ci.py serve-docs' and visiting:"
+        " http://localhost:8000 in your browser.",
+        bold=True,
+    )
 
 
 def serve_docs(directory: str = "_docs") -> None: