drop: Add --batch and --json options.

doc/git-annex-drop.mdwn

@@ -61,6 +61,16 @@ safe to do so.
   when git-annex has to contact remotes to check if it can drop files.
   For example: `-J4`  
 
+* `--batch`
+
+  Enables batch mode, in which lines containing names of files to drop
+  are read from stdin.
+
+* `--json`
+
+  Enable JSON output. This is intended to be parsed by programs that use
+  git-annex. Each line of output is a JSON object.
+
 # SEE ALSO
 
 [[git-annex]](1)

doc/todo/batch_get__47__drop__47__etc.mdwn

@@ -1,3 +1,6 @@
 in the spirit of [[todo/--batch_for_add/]], [[todo/--batch_for_info/]], [[todo/--batch_for_find/]] and [[todo/--batch_for_whereis/]], why not add `--batch` to get/drop/import operations?
 
 I am writing a script to get a bunch of arbitrary files and i want to avoid the overhead of running git-annex multiple times. I know i can use `annex.alwayscommit=false` but that is rather counter-intuitive as well. --[[anarcat]]
+
+> [[done]] for add and drop. (Not for import, but if someone requests it
+> with a use case we'll see.) --[[Joey]] 

doc/todo/drop_--batch.mdwn

@@ -1,3 +1,6 @@
 There is a dropkey --batch, so I guess I could workaround but probably would be nice for consistency to have --batch mode for drop itself as well
 
 [[!meta author=yoh]]
+
+> [[done]]; went ahead and added drop --batch to be symmetric with get
+> --batch. --[[Joey]]