avoid exporting non-annexed symlinks

So that importing does not replace them with plain files.

This works similarly to how the previous handling of submodules and
matchers did, except that annexed symlinks still get exported as plain
files of course, it's only non-annexed symlinks that it does not make sense
to export.

When symlinks have previously been exported, updating the export will
unexport them after upgrading to this commit.

Sponsored-by: Kevin Mueller on Patreon

CHANGELOG

@@ -1,3 +1,11 @@
+git-annex (8.20211232) UNRELEASED; urgency=medium
+
+  * export: When a non-annexed symlink is in the tree to be exported, skip it.
+  * import: When the previously exported tree contained a non-annexed symlink,
+    preserve it in the imported tree so it does not get deleted.
+
+ -- Joey Hess <id@joeyh.name>  Mon, 03 Jan 2022 14:01:14 -0400
+
 git-annex (8.20211231) upstream; urgency=medium
 
   * Improved support for using git-annex in a read-only repository,

Command/Export.hs

@@ -479,7 +479,8 @@ removeEmptyDirectories r db loc ks
 newtype ExportFiltered t = ExportFiltered t
 
 -- | Filters the tree to annexed files that are preferred content of the
--- remote, and also including non-annexed files, but not submodules.
+-- remote, and also including non-annexed files, but not submodules or
+-- non-annexed symlinks.
 --
 -- A log is written with tree items that were filtered out, so they can
 -- be added back in when importing from the remote.
@@ -505,17 +506,28 @@ filterExport r tree = logExportExcluded (uuid r) $ \logwriter -> do
 		case toTreeItemType mode of
 			-- Don't export submodule entries.
 			Just TreeSubmodule -> excluded
-			_ -> case mmatcher of
-				Nothing -> return (Just ti)
-				Just matcher -> catKey sha >>= \case
-					Just k -> checkmatcher matcher k
-					-- Always export non-annexed files.
-					Nothing -> return (Just ti)
+			Just TreeSymlink -> checkkey True
+			_ -> checkkey False
 	  where
 		excluded = do
 			() <- liftIO $ logwriter ti
 			return Nothing
 
+		checkkey issymlink =
+			case mmatcher of
+				Nothing
+					| issymlink -> catKey sha >>= \case
+						Just _ -> return (Just ti)
+						Nothing
+							| issymlink -> excluded
+							| otherwise -> return (Just ti)
+					| otherwise -> return (Just ti)
+				Just matcher -> catKey sha >>= \case
+					Just k -> checkmatcher matcher k
+					Nothing
+						| issymlink -> excluded
+						| otherwise -> return (Just ti)
+
 		checkmatcher matcher k = do
 			let mi = MatchingInfo $ ProvidedInfo
 				{ providedFilePath = Just $

doc/bugs/adb_replaces_symlinks_by_plain_text_files.mdwn

@@ -26,3 +26,5 @@ Don't do anything if they are the same.
 Replace symlink by actual file if they differ.
 
 [[!meta title="export then import replaces non-annex symlinks by plain text files"]]
+
+> [[fixed|done]] by skipping syminks. --[[Joey]]