Update tox config to avoid cycle on coverage envs

The `depends` cycle detection in `tox` was flagging the combined
`coverage,coverage-clean` testenv. To avoid, break this back into two
separate testenvs.

Also, add descriptions to all testenvs.

Author: sirosen

tox.ini

@@ -8,14 +8,16 @@ labels =
   ci = py, py-format, py-json5, py-json5-format, py-pyjson5, py-pyjson5-format, py-tomli, py-tomli-format, coverage
 
 envlist =
-    cov-{clean,combine,report}
+    cov_clean
     py{311,310,39,38,37}
     py{37,310}-{tomli}{,-format}
     py{37,311}-{json5,pyjson5}
+    cov
 skip_missing_interpreters = true
-minversion = 3.0.0
+minversion = 4.0.0
 
 [testenv]
+description = "run tests with pytest"
 usedevelop = true
 extras = dev
 deps =
@@ -25,25 +27,31 @@ deps =
     format: jsonschema[format]
 commands = coverage run -m pytest {posargs}
 depends =
-    py{,37,38,39,310,311}{,-json5,-pyjson5,-tomli}: coverage-clean
-    coverage: py{,37,38,39,310,311}{,-json5,-pyjson5,-tomli}
+    py{,37,38,39,310,311}{,-json5,-pyjson5,-tomli}: cov_clean
+    cov: py{,37,38,39,310,311}{,-json5,-pyjson5,-tomli}
 
-[testenv:coverage{,-clean}]
+[testenv:cov_clean]
+description = "erase coverage data to prepare for a new run"
 deps = coverage
 skip_install = true
-commands_pre =
-    !clean: coverage combine
-commands =
-    clean: coverage erase
-    !clean: coverage report --skip-covered
+commands = coverage erase
+
+[testenv:cov]
+description = "combine and report coverage data"
+deps = coverage
+skip_install = true
+commands_pre = coverage combine
+commands = coverage report --skip-covered
 
 [testenv:mypy]
+description = "check type annotations with mypy"
 deps = mypy
        types-jsonschema
        types-requests
 commands = mypy src/ {posargs}
 
 [testenv:docs]
+description = "build docs with sphinx"
 basepython = python3.10
 extras = docs
 allowlist_externals = rm
@@ -53,6 +61,7 @@ commands_pre = rm -rf _build/
 commands = sphinx-build -d _build/doctrees -b dirhtml -W . _build/dirhtml {posargs}
 
 [testenv:twine-check]
+description = "check the metadata on a package build"
 skip_install = true
 deps = twine
        build
@@ -63,13 +72,16 @@ commands = python -m build
            twine check dist/*
 
 [testenv:vendor-schemas]
+description = "update the vendored schemas"
 deps = pre-commit
 commands = python ./scripts/vendor-schemas.py
 
 [testenv:generate-hooks-config]
+description = "update autogenerated pre-commit hooks"
 commands = python ./scripts/generate-hooks-config.py
 
 [testenv:publish-release]
+description = "build and publish to pypi"
 skip_install = true
 deps = twine
        build