Add pip_install to the build. (#435)

Updates corresponding tool instructions.

WORKSPACE

@@ -6,13 +6,21 @@ workspace(name = "carbon")
 
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
-# Add Bazel's python rules.
+# Add Bazel's python rules and set up pip.
 http_archive(
     name = "rules_python",
     sha256 = "b6d46438523a3ec0f3cead544190ee13223a52f6a6765a29eae7b7cc24cc83a0",
     url = "https://github.com/bazelbuild/rules_python/releases/download/0.1.0/rules_python-0.1.0.tar.gz",
 )
 
+load("@rules_python//python:pip.bzl", "pip_install")
+
+# Create a central repo that knows about the pip dependencies.
+pip_install(
+   name = "py_deps",
+   requirements = "//github_tools:requirements.txt",
+)
+
 # Bootstrap a Clang and LLVM toolchain.
 load("//bazel/cc_toolchains:clang_bootstrap.bzl", "bootstrap_clang_toolchain")
 

docs/project/contribution_tools.md

@@ -27,8 +27,6 @@ contributions.
     -   [Clang and LLVM](#clang-and-llvm)
     -   [Ninja](#ninja)
     -   [pre-commit](#pre-commit)
-    -   [gql](#gql)
-    -   [PyGitHub](#pygithub)
 -   [Optional tools](#optional-tools)
     -   [Carbon-maintained](#carbon-maintained)
         -   [new_proposal.py](#new_proposalpy)
@@ -229,18 +227,6 @@ git commit
 When modifying or adding pre-commit hooks, please run
 `pre-commit run --all-files` to see what changes.
 
-### gql
-
-```bash
-pip install gql
-```
-
-### PyGitHub
-
-```bash
-pip install PyGitHub
-```
-
 ## Optional tools
 
 ### Carbon-maintained
@@ -268,6 +254,19 @@ Options can be seen with `-h`. A couple key options to be aware of are:
 -   `--comments-from LOGIN`: Only print threads with comments from the given
     user. For example, use when looking for threads that you've commented on.
 
+This script may be run directly if `gql` is installed:
+
+```bash
+pip install gql
+./github_tools/pr_comments.py <PR#>
+```
+
+It may also be run using `bazel`, without installing `gql`:
+
+```bash
+bazel run //github_tools:pr_comments -- <PR#>
+```
+
 ### GitHub
 
 #### gh CLI

github_tools/BUILD

@@ -3,10 +3,12 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 load("@rules_python//python:defs.bzl", "py_binary", "py_library", "py_test")
+load("@py_deps//:requirements.bzl", "requirement")
 
 py_library(
     name = "github_helpers",
     srcs = ["github_helpers.py"],
+    deps = [requirement("gql")],
 )
 
 py_test(
@@ -34,7 +36,10 @@ py_binary(
     name = "update_label_access",
     srcs = ["update_label_access.py"],
     python_version = "PY3",
-    deps = ["github_helpers"],
+    deps = [
+        "github_helpers",
+        requirement("pygithub"),
+    ],
 )
 
 py_test(

github_tools/requirements.txt

@@ -0,0 +1,7 @@
+# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+# Exceptions. See /LICENSE for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+# Python dependencies, consumed by /WORKSPACE.
+gql
+PyGitHub