Initial support for efficient sub-file incrementals.

[cumulus.git] / doc / format.txt

diff --git a/doc/format.txt b/doc/format.txt
index 7449681..66c6814 100644 (file)
--- a/doc/format.txt
+++ b/doc/format.txt
@@ -116,7 +116,11 @@ is invalid to select using the slice syntax a range of bytes that does
 not fall within the original object.  The slice specification should be
 appended to an object name, for example:
     a704eeae-97f2-4f30-91a4-d4473956366b/000001ad[264+1000]
-selects only bytes 264..1263 from the original object.
+selects only bytes 264..1263 from the original object.  As an
+abbreviation, the slice syntax
+    [<length>]
+is shorthand for
+    [0+<length>]
 
 Both a checksum and a slice can be used.  In this case, the checksum is
 given first, followed by the slice.  The checksum is computed over the
@@ -130,9 +134,9 @@ special name "zero" may be used instead of segment/sequence number.
 This represents an object consisting entirely of zeroes.  The zero
 object must have a slice specification appended to indicate the size of
 the object.  For example
-    zero[0+1024]
+    zero[1024]
 represents a block consisting of 1024 null bytes.  A checksum should not
-be given.
+be given.  The slice syntax should use the abbreviated length-only form.
 
 
 FILE METADATA LISTING
@@ -282,3 +286,6 @@ like the metadata listing).  The fields which are defined are:
         the snapshot descriptor file, but with extension .sha1sums
         instead of .lbs) containing SHA-1 checksums of all segments.
         This field contains a checksum of that file.
+    Intent: Informational; records the value of the --intent flag when
+        the snapshot was created, and can be used when determining which
+        snapshots to later delete.