add chunk metadata to Key

Added new fields for chunk number, and chunk size. These will not appear
in normal keys ever, but will be used for chunked data stored on special
remotes.

This commit was sponsored by Jouni K Seppanen.

1 files changed, 6 insertions, 3 deletions

diff --git a/doc/internals/key_format.mdwn b/doc/internals/key_format.mdwn
index 17e20592c..52fb80395 100644
--- a/doc/internals/key_format.mdwn
+++ b/doc/internals/key_format.mdwn
@@ -1,6 +1,6 @@
 A git-annex key has this format:
 
-	BACKEND-sNNNN-mNNNN--NAME
+	BACKEND[-sNNNN][-mNNNN][-SNNNN-CNNNN]--NAME
 
 For example:
 
@@ -10,12 +10,15 @@ For example:
   are always upper-cased.
 * The name field at the end has a format dependent on the backend. It is
   always the last field, and is prefixed with "--". Unlike other fields,
-  it may contain "-" in its content. It should not contain newline characters;
-  otherwise nearly anything goes.
+  it may contain "-" in its content. It should not contain newline
+  characters or "/"; otherwise nearly anything goes. 
 * The "-s" field is optional, and is the size of the content in bytes.
 * The "-m" field is optional, and is the mtime of the file when it was
   added to git-annex, expressed as seconds from the epoch.
   This is currently only used by the WORM backend.
+* The "-S" and "-C" fields are only used for keys that are chunks
+  of some other key. "-S" is the size of the chunk, and "-c" is the chunk
+  number (starting at 1).
 * Other fields could be added in the future, if needed.
 
 git-annex always puts the fields in the order shown above when serializing