Added method for comparing file groups to see if they have changed since the previous backup.

2 files changed, 63 insertions, 0 deletions

diff --git a/obnam/app.py b/obnam/app.py
index 8b7ff752..6949fe78 100644
--- a/obnam/app.py
+++ b/obnam/app.py
@@ -148,6 +148,29 @@ class Application:
                 return False
         return True
 
+    def filegroup_is_unchanged(self, fg, filenames, stat=os.stat):
+        """Is a filegroup unchanged from the previous generation?
+        
+        Given a filegroup and a list of files in the current directory,
+        return True if all files in the filegroup are unchanged from
+        the previous generation.
+        
+        The optional stat argument can be used by unit tests to
+        override the use of os.stat.
+        
+        """
+        
+        for old_name in fg.get_names():
+            if old_name not in filenames:
+                return False    # file has been deleted
+
+            old_stat = fg.get_stat(old_name)
+            new_stat = stat(old_name)
+            if not self.file_is_unchanged(old_stat, new_stat):
+                return False    # file has changed
+
+        return True             # everything seems to be as before
+
     def set_prevgen_filelist(self, filelist):
         """Set the Filelist object from the previous generation.
         
diff --git a/obnam/appTests.py b/obnam/appTests.py
index 47b64578..d046be8a 100644
--- a/obnam/appTests.py
+++ b/obnam/appTests.py
@@ -199,6 +199,46 @@ class ApplicationUnchangedFileRecognitionTests(unittest.TestCase):
         self.failIf(self.app.file_is_unchanged(st1, st2))
 
 
+class ApplicationUnchangedFileGroupTests(unittest.TestCase):
+
+    def setUp(self):
+        context = obnam.context.Context()
+        self.app = obnam.Application(context)
+        self.stats = {
+            "pink": obnam.utils.make_stat_result(st_mtime=42),
+            "pretty": obnam.utils.make_stat_result(st_mtime=105),
+        }
+
+    def mock_stat(self, filename):
+        return self.stats[filename]
+
+    def mock_filegroup(self, filenames):
+        fg = obnam.obj.FileGroupObject(id=obnam.obj.object_id_new())
+        for filename in filenames:
+            st = self.mock_stat(filename)
+            fg.add_file(filename, st, None, None, None)
+        return fg
+
+    def testSameFileGroupWhenAllFilesAreIdentical(self):
+        filenames = ["pink", "pretty"]
+        fg = self.mock_filegroup(filenames)
+        self.failUnless(self.app.filegroup_is_unchanged(fg, filenames,
+                                                        stat=self.mock_stat))
+
+    def testChangedFileGroupWhenFileHasChanged(self):
+        filenames = ["pink", "pretty"]
+        fg = self.mock_filegroup(filenames)
+        self.stats["pink"] = obnam.utils.make_stat_result(st_mtime=1)
+        self.failIf(self.app.filegroup_is_unchanged(fg, filenames,
+                                                        stat=self.mock_stat))
+
+    def testChangedFileGroupWhenFileHasBeenRemoved(self):
+        filenames = ["pink", "pretty"]
+        fg = self.mock_filegroup(filenames)
+        self.failIf(self.app.filegroup_is_unchanged(fg, filenames[:1],
+                                                        stat=self.mock_stat))
+
+
 class ApplicationFindFileByNameTests(unittest.TestCase):
 
     def setUp(self):