DOC: Improve tox.ini documentation

Author: effigies

tox.ini

@@ -1,3 +1,7 @@
+# This file encodes a lot of our intended support range, as well as some
+# details about dependency availability.
+#
+# The majority of the information is contained in tox.envlist and testenv.deps.
 [tox]
 requires =
   tox>=4
@@ -16,6 +20,7 @@ envlist =
   typecheck
 skip_missing_interpreters = true
 
+# Configuration that allows us to split tests across GitHub runners effectively
 [gh-actions]
 python =
   3.8: py38
@@ -35,14 +40,8 @@ ARCH =
   x64: x64
   x86: x86
 
-CHECK =
-  build: build
-  doctest: doctest
-  style: style
-  typecheck: typecheck
-
 [testenv]
-description = Typical pytest invocation with coverage
+description = Pytest with coverage
 labels = test
 install_command =
   python -I -m pip install \
@@ -96,7 +95,7 @@ commands =
     --pyargs nibabel {posargs:-n auto}
 
 [testenv:install]
-description = "Install and verify imports succeed"
+description = Install and verify import succeeds
 labels = test
 deps =
 extras =
@@ -105,15 +104,15 @@ commands =
   python -c "import nibabel; print(nibabel.__version__)"
 
 [testenv:docs]
-description = Typical pytest invocation with coverage
+description = Build documentation site
 labels = docs
 allowlist_externals = make
 extras = doc
 commands =
   make -C doc html
 
 [testenv:doctest]
-description = Typical pytest invocation with coverage
+description = Run doctests in documentation site
 labels = docs
 allowlist_externals = make
 extras =