Change morph to reduce loogign of the environment

Added function log_dict_diff to identify and record changes in dicts
to the debug log

This new function was then implemented in app.py to log changes in the
environment

2 files changed, 20 insertions, 2 deletions

diff --git a/morphlib/app.py b/morphlib/app.py
index 21e18e32..87710ee5 100755
--- a/morphlib/app.py
+++ b/morphlib/app.py
@@ -395,8 +395,9 @@ class Morph(cliapp.Application):
                     chatty=True)
 
         # Log the environment.
-        for name in kwargs['env']:
-            logging.debug('environment: %s=%s' % (name, kwargs['env'][name]))
+        prev = getattr(self, 'prev_env', {})
+        morphlib.util.log_dict_diff(kwargs['env'], prev)
+        self.prev_env = kwargs['env']
 
         # run the command line
         return cliapp.Application.runcmd(self, argv, *args, **kwargs)
diff --git a/morphlib/util.py b/morphlib/util.py
index c832a141..5aa00293 100644
--- a/morphlib/util.py
+++ b/morphlib/util.py
@@ -16,6 +16,7 @@
 import re
 
 import morphlib
+import logging
 
 '''Utility functions for morph.'''
 
@@ -170,6 +171,22 @@ def new_repo_caches(app):  # pragma: no cover
     return lrc, rrc
 
 
+def log_dict_diff(cur, pre):
+    '''Log the differences between two dicts to debug log'''
+    dictA = cur
+    dictB = pre
+    for key in dictA.keys():
+        if key not in dictB:
+            logging.debug("New environment: %s = %s" % (key, dictA[key]))
+        elif dictA[key] != dictB[key]:
+            logging.debug(
+                "Environment changed: %(key)s = %(valA)s to %(key)s = %(valB)s"
+                % {"key": key, "valA": dictA[key], "valB": dictB[key]})
+    for key in dictB.keys():
+        if key not in dictA:
+            logging.debug("Environment removed:  %s = %s" % (key, dictB[key]))
+
+
 # This acquired from rdiff-backup which is GPLv2+ and a patch from 2011
 # which has not yet been merged, combined with a tad of tidying from us.
 def copyfileobj(inputfp, outputfp, blocksize=1024*1024):  # pragma: no cover