pre-commit: Avoid committing the git-annex branch

Except when a commit is made in a view, which changes metadata.

Make the assistant commit the git-annex branch after git commit of working
tree changes.

This allows using the annex.commitmessage-command in the assistant to
generate a commit message for the git-annex branch that relies on state
gathered during the commit of the working tree. Eg, it might reuse the
commit message.

Note that, when not using the assistant, a git-annex add still commits
the git-annex branch, so such a annex.commitmessage-command set up would
not work then. But if someone is using the assistant and wants
programmatic control over commit messages, this is useful. Someone not
using the assistant can get the same result by using annex.alwayscommit=false
during the git-annex add, and git-annex merge after they git commit.

pre-commit was never really intended to commit the git-annex branch
(except after recording changed metadata), but the assistant did sort of
rely on it. It does later commit the git-annex branch before pushing to
remotes, but I didn't want to risk building up lots of uncommitted changes
to it if that didn't happen frequently.

Sponsored-by: the NIH-funded NICEMAN (ReproNim TR&D3) project

Command/PreCommit.hs

@@ -1,6 +1,6 @@
 {- git-annex command
  -
- - Copyright 2010-2014 Joey Hess <id@joeyh.name>
+ - Copyright 2010-2024 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -20,12 +20,14 @@ import Logs.View
 import Logs.MetaData
 import Types.View
 import Types.MetaData
+import qualified Annex
+import qualified Annex.Branch
 
 import qualified Data.Set as S
 import qualified Data.Text as T
 
 cmd :: Command
-cmd = command "pre-commit" SectionPlumbing
+cmd = noCommit $ command "pre-commit" SectionPlumbing
 	"run by git pre-commit hook"
 	paramPaths
 	(withParams seek)
@@ -47,9 +49,14 @@ seek ps = do
 	-- committing changes to a view updates metadata
 	currentView >>= \case
 		Nothing -> noop
-		Just (v, _madj) -> withViewChanges
-			(addViewMetaData v)
-			(removeViewMetaData v)
+		Just (v, _madj) -> do
+			withViewChanges
+				(addViewMetaData v)
+				(removeViewMetaData v)
+			-- Manually commit in this case, because
+			-- noCommit prevents automatic commit.
+			whenM (annexAlwaysCommit <$> Annex.getGitConfig) $
+				Annex.Branch.commit =<< Annex.Branch.commitMessage
 
 addViewMetaData :: View -> ViewedFile -> Key -> CommandStart
 addViewMetaData v f k = starting "metadata" ai si $