test: more flexibility in setting a static context locally

Author: nedbat

Diff for: igor.py

@@ -163,6 +163,8 @@ def run_tests_with_coverage(tracer, *runner_args):
     os.environ['COVERAGE_HOME'] = os.getcwd()
     context = os.environ.get('COVERAGE_CONTEXT')
     if context:
+        if context[0] == "$":
+            context = os.environ[context[1:]]
         os.environ['COVERAGE_CONTEXT'] = context + "." + tracer
 
     # Create the .pth file that will let us measure coverage in sub-processes.

Diff for: metacov.ini

@@ -16,7 +16,7 @@ source =
     ${COVERAGE_HOME-.}/tests
 # $set_env.py: COVERAGE_DYNCTX - Set to 'test_function' for who-tests-what
 dynamic_context = ${COVERAGE_DYNCTX-none}
-# $set_env.py: COVERAGE_CONTEXT - Set to a static context for this run
+# $set_env.py: COVERAGE_CONTEXT - Static context for this run (or $ENV_VAR like $TOX_ENV_NAME)
 context = ${COVERAGE_CONTEXT-none}
 
 [report]