better timestamp format

Logs/MetaData.hs

@@ -75,11 +75,9 @@ getCurrentMetaData k = do
 	-- Makes each field have the timestamp as its value.
 	genlastchanged l =
 		let MetaData m = value l
-		    ts = S.singleton $ toMetaValue $ 
-		    	formatTime defaultTimeLocale "%s" $
-				posixSecondsToUTCTime $
-					changed l
+		    ts = S.singleton $ toMetaValue $ showts $ changed l
 		in M.map (const ts) m
+	showts = formatTime defaultTimeLocale "%F@%H-%M-%S" . posixSecondsToUTCTime
 
 {- Adds in some metadata, which can override existing values, or unset
  - them, but otherwise leaves any existing metadata as-is. -}

doc/metadata.mdwn

@@ -29,8 +29,8 @@ Here are some metadata fields that git-annex has special support for:
 * `year`, `month` - When this particular version of the file came into
   being.
 * `$field-lastchanged` - This is automatically maintained for each
-  field that's set, and gives the time stamp (since the Unix epoch)
-  of the most recent change to the field. It cannot be modified directly.
+  field that's set, and gives the date and time of the most recent
+  change to the field. It cannot be modified directly.
 
 To make git-annex automatically set the year and month when adding files,
 run `git config annex.genmetadata true`. Also, see