cli (blog): preserve existing item fields on set -i + attachments fixes:

- `set -i` was replacing all fields of any existing item, losing tags, attachments,
  publication date, etc. It now fetches the existing item if any, and starts from its
  data. `-r/--replace` can be used to force a full replacement (and avoid fetching old
  item).
- `--attachment` uses `action="extend"` so multiple `-a` can be used.
- Fix attachement data key (`url` -> `sources`).

libervia/cli/cmd_blog.py

@@ -39,6 +39,7 @@ from libervia.backend.tools.common import data_format
 from libervia.backend.tools.common.ansi import ANSI as A
 from libervia.cli import common
 from libervia.cli.constants import Const as C
+from libervia.frontends.bridge.bridge_frontend import BridgeException
 
 from . import base, cmd_pubsub
 
@@ -145,6 +146,23 @@ class AltLinkAction(argparse.Action):
 class BlogPublishCommon:
     """handle common option for publising commands (Set and Edit)"""
 
+    async def get_existing_item(self, service, node, item):
+        """Fetch the data of an existing item from the pubsub service.
+
+        @param service: JID of the pubsub service (None for PEP)
+        @param node: identifier of the pubsub node (None for the default one)
+        @param item: ID of the item to fetch (None for the latest item)
+        @return: deserialised data of the item
+        @raise BridgeException: if the item can't be fetched (e.g. "item-not-found")
+        """
+        items = [item] if item else []
+        mb_data = data_format.deserialise(
+            await self.host.bridge.mb_get(
+                service, node, 1, items, data_format.serialise({}), self.profile
+            )
+        )
+        return mb_data["items"][0]
+
     async def get_current_syntax(self):
         """Retrieve current_syntax
 
@@ -190,6 +208,7 @@ class BlogPublishCommon:
             "-a",
             "--attachment",
             dest="attachments",
+            action="extend",
             nargs="+",
             help=_("attachment in the form URL [metadata_name=value]"),
         )
@@ -282,13 +301,13 @@ class BlogPublishCommon:
                             f" accepted): {arg}"
                         )
                     if attachment:
-                        # if we hae a new URL, we have a new attachment
+                        # if we have a new URL, we have a new attachment
                         attachments.append(attachment)
                         attachment = {}
-                    attachment["url"] = arg
+                    attachment["sources"] = [{"url": arg}]
                 else:
                     # we should have a metadata
-                    if "url" not in attachment:
+                    if "sources" not in attachment:
                         self.parser.error(
                             "you must to specify an URL before any metadata in "
                             "--attachment"
@@ -351,13 +370,40 @@ class Set(base.CommandBase, BlogPublishCommon):
 
     def add_parser_options(self):
         BlogPublishCommon.add_parser_options(self)
+        self.parser.add_argument(
+            "-r",
+            "--replace",
+            action="store_true",
+            help=_(
+                "don't fetch the existing item, replace all its fields with "
+                "the given ones (only used with -i)"
+            ),
+        )
 
     async def start(self):
         self.current_syntax = await self.get_current_syntax()
         self.pubsub_item = self.args.item
-        mb_data = {
+        if self.args.replace and not self.pubsub_item:
-            "service": self.args.service or None,
+            self.parser.error("--replace can only be used with -i")
-        }
+        mb_data = {}
+        if self.pubsub_item and not self.args.replace:
+            # start from the existing item data, so fields not given on the command line
+            # (tags, attachments, publication date, etc.) are kept
+            try:
+                existing = await self.get_existing_item(
+                    self.args.service, self.args.node, self.pubsub_item
+                )
+            except BridgeException as e:
+                if e.condition == "item-not-found":
+                    self.disp(f"item {self.pubsub_item!r} not found, creating a new one")
+                else:
+                    self.disp(f"can't get item: {e}", error=True)
+                    self.host.quit(C.EXIT_BRIDGE_ERRBACK)
+            else:
+                for key in KEY_TO_REMOVE_METADATA:
+                    existing.pop(key, None)
+                mb_data.update(existing)
+        mb_data["service"] = self.args.service or None
         if self.args.node:
             mb_data["node"] = self.args.node
         self.set_mb_data_from_args(mb_data)
@@ -731,14 +777,7 @@ class Edit(base.CommandBase, BlogPublishCommon, common.BaseEdit):
         return SYNTAX_EXT.get(self.current_syntax, SYNTAX_EXT[""])
 
     async def get_item_data(self, service, node, item):
-        items = [item] if item else []
+        item = await self.get_existing_item(service, node, item)
-
-        mb_data = data_format.deserialise(
-            await self.host.bridge.mb_get(
-                service, node, 1, items, data_format.serialise({}), self.profile
-            )
-        )
-        item = mb_data["items"][0]
 
         try:
             content = item["content_xhtml"]