pre-commit: Update metadata when committing changes to annexed files within a view.

So the user can now switch to a view and then move files around within it
to manage metadata. For example, moving a file into a new directory
when in the tags=* view adds a tag to it.

Implementation is fairly efficient. One diff-index, which is no more
expensive than the first stage of a git commit, followed by possibly
some cat-file --batch traffic to find the key (when deleting a file).
Very similar to what's done in direct mode when committing. And like
direct mode when updating the WC after a merge, it has to buffer the
diff-tree values in order to make 2 passes over them.

When not in a view, pre-commit now does one extra git symbolic-ref,
which is tiny overhead.

This commit was sponsored by Andrew Eskridge.

6 files changed, 103 insertions, 23 deletions

diff --git a/Annex/View.hs b/Annex/View.hs
index 6db31ce92..abf8f073e 100644
--- a/Annex/View.hs
+++ b/Annex/View.hs
@@ -13,19 +13,25 @@ import Common.Annex
 import Types.View
 import Types.MetaData
 import qualified Git
-import qualified Git.DiffTree
+import qualified Git.DiffTree as DiffTree
 import qualified Git.Branch
 import qualified Git.LsFiles
+import qualified Git.Ref
 import Git.UpdateIndex
 import Git.Sha
 import Git.HashObject
 import Git.Types
+import Git.FilePath
 import qualified Backend
 import Annex.Index
 import Annex.Link
+import Annex.CatFile
 import Logs.MetaData
 import Logs.View
 import Utility.FileMode
+import Types.Command
+import Config
+import CmdLine.Action
 
 import qualified Data.Set as S
 import System.Path.WildMatch
@@ -337,14 +343,50 @@ applyView' mkfileview view = do
  -}
 updateView :: View -> Git.Ref -> Git.Ref -> Annex Git.Branch
 updateView view ref oldref = genViewBranch view $ do
-	(diffs, cleanup) <- inRepo $ Git.DiffTree.diffTree oldref ref
+	(diffs, cleanup) <- inRepo $ DiffTree.diffTree oldref ref
 	forM_ diffs go
 	void $ liftIO cleanup
   where
 	go diff
-		| Git.DiffTree.dstsha diff == nullSha = error "TODO delete file"
+		| DiffTree.dstsha diff == nullSha = error "TODO delete file"
 		| otherwise = error "TODO add file"
 
+{- Diff between currently checked out branch and staged changes, and
+ - update metadata to reflect the changes that are being committed to the
+ - view.
+ -
+ - Adding a file to a directory adds the metadata represented by
+ - that directory to the file, and removing a file from a directory
+ - removes the metadata.
+ -
+ - Note that removes must be handled before adds. This is so
+ - that moving a file from x/foo/ to x/bar/ adds back the metadata for x.
+ -}
+withViewChanges :: (FileView -> Key -> CommandStart) -> (FileView -> Key -> CommandStart) -> Annex ()
+withViewChanges addmeta removemeta = do
+	makeabs <- flip fromTopFilePath <$> gitRepo
+	(diffs, cleanup) <- inRepo $ DiffTree.diffIndex Git.Ref.headRef
+	forM_ diffs handleremovals
+	forM_ diffs (handleadds makeabs)
+	void $ liftIO cleanup
+  where
+	handleremovals item
+		| DiffTree.srcsha item /= nullSha =
+			handle item removemeta
+				=<< catKey (DiffTree.srcsha item) (DiffTree.srcmode item)
+		| otherwise = noop
+	handleadds makeabs item
+		| DiffTree.dstsha item /= nullSha = 
+			handle item addmeta
+				=<< ifM isDirect
+					( catKey (DiffTree.dstsha item) (DiffTree.dstmode item)
+					-- optimisation
+					, isAnnexLink $ makeabs $ DiffTree.file item
+					)
+		| otherwise = noop
+	handle item a = maybe noop
+		(void . commandAction . a (getTopFilePath $ DiffTree.file item))
+
 {- Generates a branch for a view. This is done using a different index
  - file. An action is run to stage the files that will be in the branch.
  - Then a commit is made, to the view branch. The view branch is not
diff --git a/Command/PreCommit.hs b/Command/PreCommit.hs
index 388d065c0..4b90b5c2e 100644
--- a/Command/PreCommit.hs
+++ b/Command/PreCommit.hs
@@ -1,6 +1,6 @@
 {- git-annex command
  -
- - Copyright 2010, 2013 Joey Hess <joey@kitenet.net>
+ - Copyright 2010-2014 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -13,6 +13,13 @@ import Config
 import qualified Command.Add
 import qualified Command.Fix
 import Annex.Direct
+import Annex.View
+import Logs.View
+import Logs.MetaData
+import Types.View
+import Types.MetaData
+
+import qualified Data.Set as S
 
 def :: [Command]
 def = [command "pre-commit" paramPaths seek SectionPlumbing
@@ -27,13 +34,45 @@ seek ps = ifM isDirect
 		withFilesToBeCommitted (whenAnnexed Command.Fix.start) ps
 		-- inject unlocked files into the annex
 		withFilesUnlockedToBeCommitted startIndirect ps
+		-- committing changes to a view updates metadata
+		mv <- currentView
+		case mv of
+			Nothing -> noop
+			Just v -> withViewChanges
+				(addViewMetaData v)
+				(removeViewMetaData v)
 	)
 
 startIndirect :: FilePath -> CommandStart
-startIndirect file = next $ do
-	unlessM (callCommandAction $ Command.Add.start file) $
-		error $ "failed to add " ++ file ++ "; canceling commit"
+startIndirect f = next $ do
+	unlessM (callCommandAction $ Command.Add.start f) $
+		error $ "failed to add " ++ f ++ "; canceling commit"
 	next $ return True
 
 startDirect :: [String] -> CommandStart
 startDirect _ = next $ next $ preCommitDirect
+
+addViewMetaData :: View -> FileView -> Key -> CommandStart
+addViewMetaData v f k = do
+	showStart "metadata" f
+	next $ next $ changeMetaData k $ fromView v f
+
+removeViewMetaData :: View -> FileView -> Key -> CommandStart
+removeViewMetaData v f k = do
+	showStart "metadata" f
+	next $ next $ changeMetaData k $ unsetMetaData $ fromView v f
+
+changeMetaData :: Key -> MetaData -> CommandCleanup
+changeMetaData k metadata = do
+	showMetaDataChange metadata
+	addMetaData k metadata
+	return True
+
+showMetaDataChange :: MetaData -> Annex ()
+showMetaDataChange = showLongNote . unlines . concatMap showmeta . fromMetaData
+  where
+	showmeta (f, vs) = map (showmetavalue f) $ S.toList vs
+	showmetavalue f v = fromMetaField f ++ showset v ++ "=" ++ fromMetaValue v
+	showset v
+		| isSet v = "+"
+		| otherwise = "-"
diff --git a/Logs/MetaData.hs b/Logs/MetaData.hs
index a959743df..807b50afa 100644
--- a/Logs/MetaData.hs
+++ b/Logs/MetaData.hs
@@ -28,8 +28,6 @@
 module Logs.MetaData (
 	getCurrentMetaData,
 	getMetaData,
-	setMetaData,
-	unsetMetaData,
 	addMetaData,
 	addMetaData',
 	currentMetaData,
@@ -58,16 +56,6 @@ getCurrentMetaData = currentMetaData . collect <$$> getMetaData
   where
 	collect = foldl' unionMetaData newMetaData . map value . S.toAscList
 
-setMetaData :: Key -> MetaField -> String -> Annex ()
-setMetaData = setMetaData' True
-
-unsetMetaData :: Key -> MetaField -> String -> Annex ()
-unsetMetaData = setMetaData' False
-
-setMetaData' :: Bool -> Key -> MetaField -> String -> Annex ()
-setMetaData' isset k field s = addMetaData k $
-	updateMetaData field (mkMetaValue (CurrentlySet isset) s) newMetaData
-
 {- Adds in some metadata, which can override existing values, or unset
  - them, but otherwise leaves any existing metadata as-is. -}
 addMetaData :: Key -> MetaData -> Annex ()
diff --git a/Types/MetaData.hs b/Types/MetaData.hs
index 601757315..617c122a6 100644
--- a/Types/MetaData.hs
+++ b/Types/MetaData.hs
@@ -22,12 +22,14 @@ module Types.MetaData (
 	toMetaValue,
 	mkMetaValue,
 	unsetMetaValue,
+	unsetMetaData,
 	fromMetaValue,
 	fromMetaData,
 	newMetaData,
 	updateMetaData,
 	unionMetaData,
 	differenceMetaData,
+	isSet,
 	currentMetaData,
 	currentMetaDataValues,
 	metaDataValues,
@@ -137,6 +139,10 @@ mkMetaValue = MetaValue
 unsetMetaValue :: MetaValue -> MetaValue
 unsetMetaValue (MetaValue _ s) = MetaValue (CurrentlySet False) s
 
+{- Marks all MetaValues as no longer currently set. -}
+unsetMetaData :: MetaData -> MetaData
+unsetMetaData (MetaData m) = MetaData $ M.map (S.map unsetMetaValue) m
+
 fromMetaField :: MetaField -> String
 fromMetaField (MetaField f) = f
 
diff --git a/debian/changelog b/debian/changelog
index f1afdb821..36ed0b4d5 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -8,6 +8,8 @@ git-annex (5.20140211) UNRELEASED; urgency=medium
   * view: New command that creates and checks out a branch that provides
     a structured view of selected metadata.
   * vadd, vpop, vcycle: New commands for operating within views.
+  * pre-commit: Update metadata when committing changes to annexed files
+    within a view.
   * 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.
diff --git a/doc/git-annex.mdwn b/doc/git-annex.mdwn
index a5f73ac8e..cdd59ef9c 100644
--- a/doc/git-annex.mdwn
+++ b/doc/git-annex.mdwn
@@ -321,10 +321,12 @@ subdirectories).
   shown in the view.
   
   Multiple values for a metadata field can be specified, either by using
-  a glob (field="\*") or by listing each wanted value. 
+  a glob (field="\*") or by listing each wanted value. The resulting view
+  will put files in subdirectories according to the value of their fields.
   
-  When multiple field values match, the view branch will have a
-  subdirectory for each value.
+  Once within a view, you can make additional subdirectories, and
+  copy or move files into them. When you commit, the metadata will
+  be updated to correspond to your changes.
 
 * `vpop [N]`
 
@@ -801,7 +803,8 @@ subdirectories).
 
   Fixes up symlinks that are staged as part of a commit, to ensure they
   point to annexed content. Also handles injecting changes to unlocked
-  files into the annex.
+  files into the annex. When in a view, updates metadata to reflect changes
+  made to files in the view.
 
 * `lookupkey [file ...]`