diff -Nru diffoscope-136/debian/changelog diffoscope-137/debian/changelog
--- diffoscope-136/debian/changelog	2020-01-24 15:38:57.000000000 +0000
+++ diffoscope-137/debian/changelog	2020-02-18 17:15:59.000000000 +0000
@@ -1,3 +1,14 @@
+diffoscope (137) unstable; urgency=medium
+
+  * Also extract classes2.dex, classes3.dex etc. from .apk files.
+    (Closes: reproducible-builds/diffoscope#88)
+  * Add generalised support for "ignoring" returncodes and move special-casing
+    of returncodes in the zip comparator to this.
+  * Accommodate sng returning with a UNIX exit code of 1 even if there minor
+    errors in the file (discovered via #950806).
+
+ -- Chris Lamb <lamby@debian.org>  Tue, 18 Feb 2020 17:15:59 +0000
+
 diffoscope (136) unstable; urgency=medium
 
   [ Chris Lamb ]
diff -Nru diffoscope-136/diffoscope/comparators/apk.py diffoscope-137/diffoscope/comparators/apk.py
--- diffoscope-136/diffoscope/comparators/apk.py	2020-01-24 15:38:57.000000000 +0000
+++ diffoscope-137/diffoscope/comparators/apk.py	2020-02-18 17:15:59.000000000 +0000
@@ -20,6 +20,7 @@
 import re
 import os.path
 import logging
+import itertools
 import subprocess
 
 from diffoscope.tools import tool_required
@@ -74,6 +75,23 @@
                 stdout=subprocess.PIPE,
             )
 
+        # ... including "classes2.dex", "classes3.dex", etc.
+        for x in itertools.count(2):
+            try:
+                subprocess.check_call(
+                    (
+                        'unzip',
+                        '-d',
+                        self._unpacked,
+                        self.source.path,
+                        'classes{}.dex'.format(x),
+                    ),
+                    stderr=subprocess.PIPE,
+                    stdout=subprocess.PIPE,
+                )
+            except subprocess.CalledProcessError:
+                break
+
         for root, _, files in os.walk(self._unpacked):
             current_dir = []
 
diff -Nru diffoscope-136/diffoscope/comparators/png.py diffoscope-137/diffoscope/comparators/png.py
--- diffoscope-136/diffoscope/comparators/png.py	2020-01-24 15:38:57.000000000 +0000
+++ diffoscope-137/diffoscope/comparators/png.py	2020-02-18 17:15:59.000000000 +0000
@@ -33,6 +33,9 @@
 
 
 class Sng(Command):
+    # sng will return 1 if there are even minor errors in the file
+    VALID_RETURNCODES = {0, 1}
+
     @tool_required('sng')
     def cmdline(self):
         return ['sng']
diff -Nru diffoscope-136/diffoscope/comparators/utils/command.py diffoscope-137/diffoscope/comparators/utils/command.py
--- diffoscope-136/diffoscope/comparators/utils/command.py	2020-01-24 15:38:57.000000000 +0000
+++ diffoscope-137/diffoscope/comparators/utils/command.py	2020-02-18 17:15:59.000000000 +0000
@@ -30,6 +30,7 @@
 class Command(metaclass=abc.ABCMeta):
     MASK_STDERR = False
     MAX_STDERR_LINES = 50
+    VALID_RETURNCODES = {0}
 
     def __init__(self, path):
         self._path = path
@@ -109,7 +110,12 @@
 
     @property
     def returncode(self):
-        return self._process.returncode
+        val = self._process.returncode
+
+        if val in self.VALID_RETURNCODES:
+            return 0
+
+        return val
 
     @property
     def stdout(self):
diff -Nru diffoscope-136/diffoscope/comparators/zip.py diffoscope-137/diffoscope/comparators/zip.py
--- diffoscope-136/diffoscope/comparators/zip.py	2020-01-24 15:38:57.000000000 +0000
+++ diffoscope-137/diffoscope/comparators/zip.py	2020-02-18 17:15:59.000000000 +0000
@@ -36,6 +36,11 @@
 
 
 class Zipinfo(Command):
+    # zipinfo returns with an exit code of 1 or 2 when reading
+    # Mozilla-optimized or Java "jmod" ZIPs as they have non-standard headers
+    # which are safe to ignore.
+    VALID_RETURNCODES = {0, 1, 2}
+
     @tool_required('zipinfo')
     def cmdline(self):
         # zipinfo (without -v) puts warning messages (some of which contain
@@ -43,18 +48,6 @@
         # to work around it, we run it on /dev/stdin instead, seems to work ok.
         return ['zipinfo', '/dev/stdin']
 
-    @property
-    def returncode(self):
-        returncode = super().returncode
-
-        # zipinfo returns with an exit code of 1 or 2 when reading
-        # Mozilla-optimized or Java "jmod" ZIPs as they have non-standard
-        # headers which are safe to ignore.
-        if returncode in (1, 2):
-            returncode = 0
-
-        return returncode
-
     def stdin(self):
         return open(self.path, 'rb')
 
@@ -72,6 +65,9 @@
 
 
 class Zipnote(Command):
+    # zipnote returns with an exit code of 3 for invalid archives
+    VALID_RETURNCODES = {0, 3}
+
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
@@ -85,13 +81,6 @@
             shutil.copy(self.path, path)
         return ['zipnote', path]
 
-    @property
-    def returncode(self):
-        returncode = super().returncode
-
-        # zipnote returns with an exit code of 3 for invalid archives
-        return 0 if returncode == 3 else returncode
-
     def filter(self, line):
         """
         Example output from zipnote(1):
diff -Nru diffoscope-136/diffoscope/__init__.py diffoscope-137/diffoscope/__init__.py
--- diffoscope-136/diffoscope/__init__.py	2020-01-24 15:38:57.000000000 +0000
+++ diffoscope-137/diffoscope/__init__.py	2020-02-18 17:15:59.000000000 +0000
@@ -17,4 +17,4 @@
 # You should have received a copy of the GNU General Public License
 # along with diffoscope.  If not, see <https://www.gnu.org/licenses/>.
 
-VERSION = "136"
+VERSION = "137"