Don't try to instantiate a Bag instance on non-directories in is_bag.

Don't preserve `mtime` for payload files in idempotent mode. There are arguments for/against this but there is ultimately more broad utility in eliminating it. At some point there must be a tradeoff; if this information is important to preserve, idempotent mode should not be used.
Similarly, when extracting a tar-based archive, if `mtime` is set to zero (i.e. epoch), use the tarfile extraction filter to set `mtime` to None which will cause tarfile to suppress preserving the mtime in the extracted file. This should work in every version that has the back-ported extraction filter support. Python versions less than 3.8 won't be able to do this but those are deprecated and are going to be unsupported by bdbag soon.
Add Python 3.12 into GH Actions tests.
Remove travis.yml.

.github/workflows/bdbag.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
 
     steps:
     - uses: actions/checkout@v3

bdbag/bdbag_api.py

@@ -130,9 +130,10 @@ def prune_bag_manifests(bag):
 def is_bag(bag_path):
     bag = None
     try:
-        bag = bdbagit.BDBag(bag_path)
+        if os.path.isdir(bag_path):
+            bag = bdbagit.BDBag(bag_path)
     except (bdbagit.BagError, bdbagit.BagValidationError) as e:  # pragma: no cover
-        logger.warning("Exception while checking if %s is a bag: %s" % (bag_path, e))
+        logger.warning("Exception while checking if directory %s is a bag: %s" % (bag_path, e))
     return True if bag else False
 
 
@@ -382,10 +383,8 @@ def archive_bag(bag_path, bag_archiver, config_file=None, idempotent=None):
 def tar_bag_dir(bag_path, tar_file_path, tarmode, idempotent=False):
 
     def filter_mtime(tarinfo):
-        # a fixed mtime is a core requirement for a reproducible archive, but we should preserve payload file mtimes
-        if not (tarinfo.name.startswith(os.path.basename(bag_path) + "/data/") and
-                os.path.isfile(os.path.dirname(bag_path) + "/" + tarinfo.name)):
-            tarinfo.mtime = 0
+        # a fixed mtime is a core requirement for a reproducible archive
+        tarinfo.mtime = 0
         return tarinfo
 
     is_idempotent_tgz = False
@@ -434,8 +433,8 @@ def zip_bag_dir(bag_path, zip_file_path, idempotent=False):
     for e in entries:
         filepath = os.path.join(os.path.dirname(bag_path), e)
         payload_dir = os.path.join(os.path.basename(bag_path), "data", "")
-        # a fixed mtime is a core requirement for a reproducible archive, but we should preserve payload file mtimes
-        if idempotent and not (e.startswith(payload_dir) and os.path.isfile(filepath)):
+        # a fixed mtime is a core requirement for a reproducible archive
+        if idempotent:
             date_time = (1980, 1, 1, 0, 0, 0)
         else:
             st = os.stat(filepath)
@@ -506,7 +505,13 @@ def extract_bag(bag_path, output_path=None, temp=False, config_file=None):
         try:
             if isinstance(archive, tarfile.TarFile):
                 if hasattr(tarfile, 'data_filter'):
-                    archive.extractall(base_path, filter='data')
+                    # customize tarfile 'data' filter: if we encounter a tarinfo entry with a mtime of 0 (epoch), then
+                    # set mtime to None which will cause tarfile to suppress preserving the mtime for the extracted file
+                    def tar_data_filter(entry, path):
+                        if entry.mtime == 0:
+                            entry.mtime = None
+                        return tarfile.data_filter(entry, path)
+                    archive.extractall(base_path, filter=tar_data_filter)
                 else:
                     if isinstance(archive, tarfile.TarFile):
                         logger.warning('SECURITY WARNING: TAR extraction may be unsafe; consider updating Python to a '

setup.py

@@ -84,11 +84,11 @@
         "Operating System :: MacOS :: MacOS X",
         "Operating System :: Microsoft :: Windows",
         'Programming Language :: Python',
-        'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
-        'Programming Language :: Python :: 3.11'
+        'Programming Language :: Python :: 3.11',
+        'Programming Language :: Python :: 3.12'
 
     ]
 )