[pp:hash] add 'hash' post processor (#6099)

docs/configuration.rst

@@ -5586,6 +5586,63 @@ Description
     See `metadata.event`_ for a list of available events.
 
 
+hash.chunk-size
+---------------
+Type
+    ``integer``
+Default
+    ``32768``
+Description
+    Number of bytes read per chunk during file hash computation.
+
+
+hash.event
+----------
+Type
+    * ``string``
+    * ``list`` of ``strings``
+Default
+    ``"file"``
+Description
+    The event(s) for which `file hashes <hash.hashes_>`__ are computed.
+
+    See `metadata.event`_ for a list of available events.
+
+
+hash.filename
+-------------
+Type
+    * ``bool``
+Default
+    ``false``
+Description
+    Rebuild `filenames <extractor.*.filename_>`__ after computing
+    `hash digests <hash.hashes_>`__ and adding them to the metadata dict.
+
+
+hash.hashes
+-----------
+Type
+    * ``string``
+    * ``object`` (`field name` -> `hash algorithm`)
+Default
+    ``"md5,sha1"``
+Example
+    .. code:: json
+
+        "sha256:hash_sha,sha3_512:hash_sha3"
+
+    .. code:: json
+
+        {
+            "hash_sha" : "sha256",
+            "hash_sha3": "sha3_512"
+        }
+
+Description
+    Hash digests to compute.
+
+
 metadata.mode
 -------------
 Type
@@ -6694,6 +6751,8 @@ Description
         | (requires `downloader.*.part`_ = ``true`` and `extractor.*.skip`_ = ``false``)
     ``exec``
         Execute external commands
+    ``hash``
+        Compute file hash digests
     ``metadata``
         Write metadata to separate files
     ``mtime``