add vcycle command

CmdLine/GitAnnex.hs

@@ -30,6 +30,7 @@ import qualified Command.MetaData
 import qualified Command.View
 import qualified Command.VAdd
 import qualified Command.VPop
+import qualified Command.VCycle
 import qualified Command.Reinject
 import qualified Command.Fix
 import qualified Command.Init
@@ -142,6 +143,7 @@ cmds = concat
 	, Command.View.def
 	, Command.VAdd.def
 	, Command.VPop.def
+	, Command.VCycle.def
 	, Command.Fix.def
 	, Command.Fsck.def
 	, Command.Repair.def

Command/VCycle.hs

@@ -0,0 +1,45 @@
+{- git-annex command
+ -
+ - Copyright 2014 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Command.VCycle where
+
+import Common.Annex
+import Command
+import Annex.View
+import Types.View
+import Logs.View
+import Command.View (checkoutViewBranch)
+
+def :: [Command]
+def = [notBareRepo $ notDirect $
+	command "vcycle" paramNothing seek SectionUtility
+	"switch view to next layout"]
+
+seek :: CommandSeek
+seek = withNothing start
+
+start ::CommandStart
+start = go =<< currentView
+  where
+	go Nothing = error "Not in a view."
+	go (Just v) = do
+		let v' = v { viewComponents = vcycle [] (viewComponents v) }
+		if v == v'
+			then do
+				showNote "unchanged"
+				next $ next $ return True
+			else next $ perform v'
+
+	vcycle rest (c:cs)
+		| multiValue (viewFilter c) = rest ++ cs ++ [c]
+		| otherwise = vcycle (c:rest) cs
+	vcycle rest c = rest ++ c
+
+perform :: View -> CommandPerform
+perform view = do
+	branch <- narrowView view
+	next $ checkoutViewBranch view branch

debian/changelog

@@ -7,7 +7,7 @@ git-annex (5.20140211) UNRELEASED; urgency=medium
     to limit them to acting on files that have particular metadata.
   * view: New command that creates and checks out a branch that provides
     a structured view of selected metadata.
-  * vadd, vpop: New commands for operating within views.
+  * vadd, vpop, vcycle: New commands for operating within views.
   * Add progress display for transfers to/from external special remotes.
   * Windows webapp: Can set up box.com, Amazon S3, and rsync.net remotes
   * Windows webapp: Can create repos on removable drives.

doc/git-annex.mdwn

@@ -326,14 +326,21 @@ subdirectories).
   When multiple field values match, the view branch will have a
   subdirectory for each value.
 
+* `vpop`
+
+  Switches from the currently active view back to the previous view.
+  Or, from the first view back to original branch.
+
 * `vadd [field=value ...] [tag ...]`
 
   Refines the currently checked out view branch, adding additional fields
   or tags.
 
-* `vpop`
+* `vcycle`
 
-  Switches from the currently active view back to the previous view.
+  When a view involves nested subdirectories, this cycles the order.
+  For example, when the view has date/author/tag, vcycle will switch
+  it to author/tag/date.
 
 # REPOSITORY SETUP COMMANDS