enable filter.annex.process in v9

This has tradeoffs, but is generally a win, and users who it causes git add to
slow down unacceptably for can just disable it again.

It needed to happen in an upgrade, since there are git-annex versions
that do not support it, and using such an old version with a v8
repository with filter.annex.process set will cause bad behavior.
By enabling it in v9, it's guaranteed that any git-annex version that
can use the repository does support it. Although, this is not a perfect
protection against problems, since an old git-annex version, if it's
used with a v9 repository, will cause git add to try to run
git-annex filter-process, which will fail. But at least, the user is
unlikely to have an old git-annex in path if they are using a v9
repository, since it won't work in that repository.

Sponsored-by: Dartmouth College's Datalad project

Config/Smudge.hs

@@ -1,6 +1,6 @@
 {- Git smudge filter configuration
  -
- - Copyright 2011-2019 Joey Hess <id@joeyh.name>
+ - Copyright 2011-2022 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -16,6 +16,7 @@ import qualified Git.Command
 import Git.Types
 import Config
 import Utility.Directory.Create
+import Annex.Version
 
 import qualified System.FilePath.ByteString as P
 
@@ -32,6 +33,8 @@ configureSmudgeFilter = unlessM (fromRepo Git.repoIsLocalBare) $ do
 
 	setConfig (ConfigKey "filter.annex.smudge") "git-annex smudge -- %f"
 	setConfig (ConfigKey "filter.annex.clean") "git-annex smudge --clean -- %f"
+	whenM (versionSupportsFilterProcess <$> getVersion)
+		configureSmudgeFilterProcess
 	lf <- Annex.fromRepo Git.attributesLocal
 	gf <- Annex.fromRepo Git.attributes
 	lfs <- readattr lf
@@ -43,6 +46,10 @@ configureSmudgeFilter = unlessM (fromRepo Git.repoIsLocalBare) $ do
   where
 	readattr = liftIO . catchDefaultIO "" . readFileStrict . fromRawFilePath
 
+configureSmudgeFilterProcess :: Annex ()
+configureSmudgeFilterProcess =
+	setConfig (ConfigKey "filter.annex.process") "git-annex filter-process"
+
 stdattr :: [String]
 stdattr =
 	[ "* filter=annex"