graft exported tree into git-annex branch

So it will be available later and elsewhere, even after GC.

I first though to use git update-index to do this, but feeding it a line
with a tree object seems to always cause it to generate a git subtree
merge. So, fell back to using the Git.Tree interface to maniupulate the
trees, and not involving the git-annex branch index file at all.

This commit was sponsored by Andreas Karlsson.

1 files changed, 24 insertions, 0 deletions

diff --git a/Logs/Export.hs b/Logs/Export.hs
index a0019a06c..1fd1460fc 100644
--- a/Logs/Export.hs
+++ b/Logs/Export.hs
@@ -12,6 +12,9 @@ import qualified Data.Map as M
 import Annex.Common
 import qualified Annex.Branch
 import qualified Git
+import qualified Git.Branch
+import Git.Tree
+import Git.FilePath
 import Logs
 import Logs.UUIDBased
 import Annex.UUID
@@ -40,6 +43,9 @@ data ExportChange = ExportChange
 -- newTreeish. This way, when multiple repositories are exporting to
 -- the same special remote, there's no conflict as long as they move
 -- forward in lock-step.
+--
+-- Also, the newTreeish is grafted into the git-annex branch. This is done
+-- to ensure that it's available later.
 recordExport :: UUID -> ExportChange -> Annex ()
 recordExport remoteuuid ec = do
 	c <- liftIO currentVectorClock
@@ -50,6 +56,7 @@ recordExport remoteuuid ec = do
 			. changeLog c u val 
 			. M.mapWithKey (updateothers c u)
 			. parseLogNew parseExportLog
+	graftTreeish (newTreeish ec)
   where
 	updateothers c u theiru le@(LogEntry _ (ExportLog t remoteuuid'))
 		| u == theiru || remoteuuid' /= remoteuuid || t `notElem` oldTreeish ec = le
@@ -65,3 +72,20 @@ parseExportLog :: String -> Maybe ExportLog
 parseExportLog s = case words s of
 	(t:u:[]) -> Just $ ExportLog (Git.Ref t) (toUUID u)
 	_ -> Nothing
+
+-- To prevent git-annex branch merge conflicts, the treeish is
+-- first grafted in and then removed in a subsequent commit.
+graftTreeish :: Git.Ref -> Annex ()
+graftTreeish treeish = do
+	branchref <- Annex.Branch.getBranch
+	Tree t <- inRepo $ getTree branchref
+	t' <- inRepo $ recordTree $ Tree $
+		RecordedSubTree (asTopFilePath graftpoint) treeish [] : t
+	commit <- inRepo $ Git.Branch.commitTree Git.Branch.AutomaticCommit
+		"export tree" [branchref] t'
+	origtree <- inRepo $ recordTree (Tree t)
+	commit' <- inRepo $ Git.Branch.commitTree Git.Branch.AutomaticCommit
+		"export tree cleanup" [commit] origtree
+	inRepo $ Git.Branch.update' Annex.Branch.fullname commit'
+  where
+	graftpoint = "export.tree"