snapshot: Documentation and comment improvements

Changes noticed while copying to similar aspects of checkpoints.
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

docs/formatsnapshot.html.in

@@ -223,11 +223,9 @@
         guest.
       </dd>
       <dt><code>parent</code></dt>
-      <dd>An optional readonly representation of the parent of this
-        snapshot.  If present, this element contains exactly one child
-        element, <code>name</code>.  This specifies the name of the
-        parent snapshot of this snapshot, and is used to represent
-        trees of snapshots.
+      <dd>Readonly, present only if this snapshot has a parent. The
+        parent name is given by the sub-element <code>name</code>. The
+        parent relationship allows tracking a tree of related snapshots.
       </dd>
       <dt><code>domain</code></dt>
       <dd>A readonly representation of the domain that this snapshot

tests/virsh-snapshot

@@ -85,7 +85,7 @@ $abs_top_builddir/tools/virsh --connect test:///default >out 2>err '
 # and snapshot-list produces timestamps
 sed 's/ *$//; s/[0-9-]\{10\} [0-9:.]* .[0-9]\{4\}/TIMESTAMP/;
    /MarkerA/,/MarkerC/d' < out > out.cooked || fail=1
-# Second part holds domain XMLs
+# Second part holds domain snapshot XMLs
 sed -n '/MarkerA/,/MarkerB/p' < out > s3.xml || fail=1
 sed -n '/MarkerB/,/MarkerC/p' < out > s2.xml || fail=1