metadata: Added -r to remove all current values of a field.

Annex/MetaData.hs

@@ -61,7 +61,7 @@ dateMetaData mtime old = MetaData $ M.fromList $ filter isnew
 parseModMeta :: String -> Either String ModMeta
 parseModMeta p = case lastMaybe f of
 	Just '+' -> AddMeta <$> mkMetaField f' <*> v
-	Just '-' -> DelMeta <$> mkMetaField f' <*> v
+	Just '-' -> DelMeta <$> mkMetaField f' <*> (Just <$> v)
 	Just '?' -> MaybeSetMeta <$> mkMetaField f' <*> v
 	_ -> SetMeta <$> mkMetaField f <*> v
   where

Command/MetaData.hs

@@ -46,10 +46,14 @@ optParser desc = MetaDataOptions
 			( long "tag" <> short 't' <> metavar "TAG"
 			<> help "set a tag"
 			))
-		<|> (DelMeta tagMetaField . toMetaValue <$> strOption
+		<|> (DelMeta tagMetaField . Just . toMetaValue <$> strOption
 			( long "untag" <> short 'u' <> metavar "TAG"
 			<> help "remove a tag"
 			))
+		<|> option (eitherReader (\f -> DelMeta <$> mkMetaField f <*> pure Nothing))
+			( long "remove"  <> short 'r' <> metavar "FIELD"
+			<> help "remove all values of a field"
+			)
 
 seek :: MetaDataOptions -> CommandSeek
 seek o = do

Types/MetaData.hs

@@ -219,9 +219,13 @@ metaDataValues f (MetaData m) = fromMaybe S.empty (M.lookup f m)
 {- Ways that existing metadata can be modified -}
 data ModMeta
 	= AddMeta MetaField MetaValue
-	| DelMeta MetaField MetaValue
-	| SetMeta MetaField MetaValue -- removes any existing values
-	| MaybeSetMeta MetaField MetaValue -- when field has no existing value
+	| DelMeta MetaField (Maybe MetaValue)
+	-- ^ delete value of a field. With Just, only that specific value
+	-- is deleted; with Nothing, all current values are deleted.
+	| SetMeta MetaField MetaValue
+	-- ^ removes any existing values
+	| MaybeSetMeta MetaField MetaValue
+	-- ^ set when field has no existing value
 	deriving (Show)
 
 {- Applies a ModMeta, generating the new MetaData.
@@ -229,7 +233,10 @@ data ModMeta
  - values set in the input metadata. It only contains changed values. -}
 modMeta :: MetaData -> ModMeta -> MetaData
 modMeta _ (AddMeta f v) = updateMetaData f v emptyMetaData
-modMeta _ (DelMeta f oldv) = updateMetaData f (unsetMetaValue oldv) emptyMetaData
+modMeta _ (DelMeta f (Just oldv)) =
+	updateMetaData f (unsetMetaValue oldv) emptyMetaData
+modMeta m (DelMeta f Nothing) = MetaData $ M.singleton f $
+	S.fromList $ map unsetMetaValue $ S.toList $ currentMetaDataValues f m
 modMeta m (SetMeta f v) = updateMetaData f v $
 	foldr (updateMetaData f) emptyMetaData $
 		map unsetMetaValue $ S.toList $ currentMetaDataValues f m

debian/changelog

@@ -1,3 +1,9 @@
+git-annex (6.20160230) UNRELEASED; urgency=medium
+
+  * metadata: Added -r to remove all current values of a field.
+
+ -- Joey Hess <id@joeyh.name>  Mon, 29 Feb 2016 13:00:30 -0400
+
 git-annex (6.20160229) unstable; urgency=medium
 
   * Update perlmagick build dependency. Closes: #789225

doc/git-annex-metadata.mdwn

@@ -19,34 +19,39 @@ When run without any -s or -t parameters, displays the current metadata.
 
 # OPTIONS
 
-* `-g field`
+* `-g field` / `--get field`
 
   Get the value(s) of a single field.
 
   The values will be output one per line, with no other output, so
   this is suitable for use in a script.
 
-* `-s field=value`
+* `-s field=value` / `--set field=value`
 
   Set a field's value, removing any old values.
 
-* `-s field+=value`
+* `-s field+=value` / `--set field+=value`
 
   Add an additional value, preserving any old values.
 
-* `-s field-=value`
-
-  Remove a value.
-
-* `-s field?=value`
+* `-s field?=value` / `--set field?=value`
 
   Set a value, but only if the field does not already have a value set.
 
-* `-t tag`
+* `-s field-=value` / `--set field-=value`
+
+  Remove a value from a field, leaving any other values that the field has
+  set.
+
+* `-r field` / `--remove field`
+
+  Remove all current values of the field.
+
+* `-t tag` / `--tag tag`
 
   Set a tag. Note that a tag is just a value of the "tag" field.
 
-* `-u tag`
+* `-u tag` / `--unset tag`
 
   Unset a tag.