cmds.secrets.lib.tar: Add module

Add a module cmds.secrets.lib.tar. Secrets handling demands treating tar archive members more individually, jw.pkg.lib.TarIo is not a good fit for that, so try with a different module. To be merged eventually.
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/cmds/secrets/lib/tar.py

@@ -0,0 +1,61 @@
+# -*- coding: utf-8 -*-
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Callable
+
+import tarfile, io
+from tarfile import TarFile
+
+from ....lib.log import *
+
+if TYPE_CHECKING:
+    from ....lib.ExecContext import ExecContext
+
+def filter(blob: bytes, path_filter: Callable[[str], bool]|None, matched: list[str]|None=None) -> bytes:
+    ret = io.BytesIO()
+    with tarfile.open(fileobj=ret, mode='w') as tf_out:
+        tf_in = TarFile(fileobj=io.BytesIO(blob))
+        for info in tf_in.getmembers():
+            if path_filter is not None and not path_filter(info.name):
+                continue
+            log(DEBUG, f'Adding {info.name}')
+            if matched is not None:
+                matched.append(info.name)
+            buf = tf_in.extractfile(info)
+            tf_out.addfile(info, buf)
+    return ret.getvalue()
+
+def rewrite(blob: bytes, rewrite_filter: Callable[[str], str]) -> bytes:
+    ret = io.BytesIO()
+    with tarfile.open(fileobj=ret, mode='w') as tf_out:
+        tf_in = TarFile(fileobj=io.BytesIO(blob))
+        for info in tf_in.getmembers():
+            new_name = rewrite_filter(info.name)
+            log(DEBUG, f'Rewriting {info.name} -> {new_name}')
+            info.name = new_name
+            buf = tf_in.extractfile(info)
+            tf_out.addfile(info, buf)
+    return ret.getvalue()
+
+def merge(blobs: Iterable[bytes], overwrite: bool=False) -> bytes:
+    ret = io.BytesIO()
+    with tarfile.open(fileobj=ret, mode='w') as tf_out:
+        for blob in blobs:
+            tf_in = TarFile(fileobj=io.BytesIO(blob))
+            existing_names = tf_out.getnames()
+            for info in tf_in.getmembers():
+                if not overwrite and info.name in existing_names:
+                    continue
+                buf = tf_in.extractfile(info)
+                tf_out.addfile(info, buf)
+    return ret.getvalue()
+
+async def extract(dst: ExecContext, blob: bytes, root: str|None=None, verbose: bool=False) -> None:
+    cmd = ['tar']
+    if root is not None:
+        cmd += ['-C', root]
+    if verbose:
+        cmd += '-v'
+    cmd += ['-x', '-f', '-']
+    await dst.run(cmd, verbose=verbose, cmd_input=blob)