check: do not create addtl. archives dir entries if we already have one

if the manifest file is missing, check generated *.1 *.2 ... archives although an entry for the correct name and id was already
present. BUG!

this is because if the manifest is lost, that does not imply
anymore that the complete archives directory is also lost, as it
did in borg 1.x.

Also improved log messages a bit.

src/borg/archive.py

@@ -1757,7 +1757,7 @@ class ArchiveChecker:
         )
 
     def rebuild_manifest(self):
-        """Rebuild the manifest object if it is missing
+        """Rebuild the manifest object and the archives list.
 
         Iterates through all objects in the repository looking for archive metadata blocks.
         """
@@ -1767,7 +1767,7 @@ class ArchiveChecker:
                 return False
             return REQUIRED_ARCHIVE_KEYS.issubset(obj)
 
-        logger.info("Rebuilding missing manifest, this might take some time...")
+        logger.info("Rebuilding missing manifest and missing archives directory entries, this might take some time...")
         # as we have lost the manifest, we do not know any more what valid item keys we had.
         # collecting any key we encounter in a damaged repo seems unwise, thus we just use
         # the hardcoded list from the source code. thus, it is not recommended to rebuild a
@@ -1775,7 +1775,10 @@ class ArchiveChecker:
         # within this repository (assuming that newer borg versions support more item keys).
         manifest = Manifest(self.key, self.repository)
         pi = ProgressIndicatorPercent(
-            total=len(self.chunks), msg="Rebuilding manifest %6.2f%%", step=0.01, msgid="check.rebuild_manifest"
+            total=len(self.chunks),
+            msg="Rebuilding manifest and archives directory %6.2f%%",
+            step=0.01,
+            msgid="check.rebuild_manifest",
         )
         for chunk_id, _ in self.chunks.iteritems():
             pi.show()
@@ -1797,19 +1800,25 @@ class ArchiveChecker:
                 archive = self.key.unpack_archive(data)
                 archive = ArchiveItem(internal_dict=archive)
                 name = archive.name
-                logger.info("Found archive %s", name)
-                if manifest.archives.exists(name):
+                logger.info(f"Found archive {name}, id {bin_to_hex(chunk_id)}.")
+                if manifest.archives.exists_name_and_id(name, chunk_id):
+                    logger.info("We already have an archives directory entry for this.")
+                elif not manifest.archives.exists(name):
+                    # no archives list entry yet and name is not taken yet, create an entry
+                    logger.warning(f"Creating archives directory entry for {name}.")
+                    manifest.archives.create(name, chunk_id, archive.time)
+                else:
+                    # we don't have an entry yet, but the name is taken by something else
                     i = 1
                     while True:
                         new_name = "%s.%d" % (name, i)
                         if not manifest.archives.exists(new_name):
                             break
                         i += 1
-                    logger.warning("Duplicate archive name %s, storing as %s", name, new_name)
-                    name = new_name
-                manifest.archives.create(name, chunk_id, archive.time)
+                    logger.warning(f"Creating archives directory entry using {new_name}.")
+                    manifest.archives.create(new_name, chunk_id, archive.time)
         pi.finish()
-        logger.info("Manifest rebuild complete.")
+        logger.info("Manifest and archives directory rebuild complete.")
         return manifest
 
     def rebuild_archives(

src/borg/manifest.py

@@ -119,6 +119,19 @@ class Archives:
         else:
             return name in self._archives
 
+    def exists_name_and_id(self, name, id):
+        # check if an archive with this name AND id exists
+        assert isinstance(name, str)
+        assert isinstance(id, bytes)
+        if not self.legacy:
+            for _, archive_info in self._infos():
+                if archive_info["name"] == name and archive_info["id"] == id:
+                    return True
+            else:
+                return False
+        else:
+            raise NotImplementedError
+
     def _infos(self):
         # yield the infos of all archives: (store_key, archive_info)
         from .helpers import msgpack