ab3cfg,main: also accept specifying stage2 mode ...

* ... via environment variables
* also print out a message when running in stage2 mode

Author: liushuyu

acbs/ab3cfg.py

@@ -5,13 +5,25 @@
 from pyparsing import ParseException # type: ignore
 
 
+def is_in_stage2_file(ab3cfg_path: str) -> bool:
+    with open(ab3cfg_path) as f:
+        vars = bashvar.eval_bashvar(f.read(), filename=ab3cfg_path)
+        stage2_val: str = vars.get('ABSTAGE2')
+        return stage2_val == '1'
+    return False
+
+
+def is_in_stage2_env() -> bool:
+    return os.environ.get('ABSTAGE2', '') == '1'
+
+
 def is_in_stage2() -> bool:
+    """
+    Return whether the current environment is in a stage2 development phase.
+    """
     ab3cfg_path: str = os.path.join(AUTOBUILD_CONF_DIR, 'ab3cfg.sh')
     try:
-        with open(ab3cfg_path) as f:
-            vars = bashvar.eval_bashvar(f.read(), filename=ab3cfg_path)
-            stage2_val: str = vars.get('ABSTAGE2')
-            return stage2_val == '1'
+        return is_in_stage2_env() or is_in_stage2_file(ab3cfg_path)
     except OSError as e:
         raise RuntimeError(f'Unable to read Autobuild config file {ab3cfg_path}.') from e
     except ParseException as e:

acbs/main.py

@@ -94,6 +94,8 @@ def build(self) -> None:
         build_timings: List[Tuple[str, float]] = []
         acbs.fetch.generate_mode = self.generate
         acbs.parser.generate_mode = self.generate
+        if self.stage2:
+            logging.info("Life-cycle: currently running in stage2 mode.")
         # begin finding and resolving dependencies
         logging.info('Searching and resolving dependencies...')
         acbs.pm.reorder_mode = self.reorder