Improve doc for using container-sync with large objects

Clarify that synced segment container names must be the same
when syncing large objects.

Also add multipart-menifest query string option to API ref
for object GETs.

Change-Id: Ib2d2a1e6c1e5eff215fc75c2b49e7d6758b17b7e
Partial-Bug: #1613681
Closes-Bug: #1613316

api-ref/source/parameters.yaml

@@ -840,7 +840,7 @@ multipart-manifest_1:
   in: query
   required: false
   type: string
-multipart-manifest_2:
+multipart-manifest_get:
   description: |
     If you include the ``multipart-manifest=get``
     query parameter and the object is a large object, the object
@@ -850,6 +850,15 @@ multipart-manifest_2:
   in: query
   required: false
   type: string
+multipart-manifest_head:
+  description: |
+    If you include the ``multipart-manifest=get`` query parameter and the
+    object is a large object, the object metadata is not returned. Instead, the
+    response headers will include the manifest metadata and for dynamic large
+    objects the ``X-Object-Manifest`` response header.
+  in: query
+  required: false
+  type: string
 path:
   description: |
     For a string value, returns the object names that

api-ref/source/storage-object-services.inc

@@ -103,7 +103,7 @@ Request
    - temp_url_sig: temp_url_sig
    - temp_url_expires: temp_url_expires
    - filename: filename
-   - multipart-manifest: multipart-manifest
+   - multipart-manifest: multipart-manifest_get
    - Range: Range
    - If-Match: If-Match
    - If-None-Match: If-None-Match
@@ -524,6 +524,7 @@ Request
    - temp_url_sig: temp_url_sig
    - temp_url_expires: temp_url_expires
    - filename: filename
+   - multipart-manifest: multipart-manifest_head
    - X-Newest: X-Newest
    - X-Trans-Id-Extra: X-Trans-Id-Extra
 

doc/source/overview_container_sync.rst

@@ -14,9 +14,13 @@ synchronization key.
 
 .. note::
 
-    If you are using the large objects feature you will need to ensure both
-    your manifest file and your segment files are synced if they happen to be
-    in different containers.
+    If you are using the large objects feature and syncing to another cluster
+    then you will need to ensure that manifest files and segment files are
+    synced. If segment files are in a different container than their manifest
+    then both the manifest's container and the segments' container must be
+    synced. The target container for synced segment files must always have the
+    same name as their source container in order for them to be resolved by
+    synced manifests.
 
 .. note::