stop symlink check once the top of the working tree is reached

Avoid complaining that a file with "is beyond a symbolic link" when the
filepath is absolute and the symlink in question is not actually inside the
git repository.

This assumes that inodes remain stable while the command is running.
I think they always will, the filesystems where they are unstable change
them across mounts. (If inodes were not stable, it would just complain about
symlinks in the path that are not inside the working tree.)

(On windows, I don't want to assume anything about inodes, they could be
random numbers for all I know. But if they were, this would still be ok, as
long as windows doesn't have symlinks that are detected by isSymbolicLink.
Which seems a fair bet.)

CHANGELOG

@@ -20,6 +20,9 @@ git-annex (8.20200720.2) UNRELEASED; urgency=medium
   * Slightly sped up the linux standalone bundle.
   * importfeed: Fix reversion that caused some '.' in filenames to be
     replaced with '_'
+  * Avoid complaining that a file with "is beyond a symbolic link"
+    when the filepath is absolute and the symlink in question is not
+    actually inside the git repository.
 
  -- Joey Hess <id@joeyh.name>  Tue, 21 Jul 2020 12:58:30 -0400
 

CmdLine/Seek.hs

@@ -445,11 +445,12 @@ workTreeItems' (AllowHidden allowhidden) ww ps = case ww of
   where
 	runcheck = do
 		currbranch <- getCurrentBranch
+		stopattop <- prepviasymlink
 		ps' <- flip filterM ps $ \p -> do
 			relf <- liftIO $ relPathCwdToFile p
 			ifM (not <$> (exists p <||> hidden currbranch relf))
 				( prob (p ++ " not found")
-				, ifM (viasymlink (upFrom relf))
+				, ifM (viasymlink stopattop (upFrom relf))
 					( prob (p ++ " is beyond a symbolic link")
 					, return True
 					)
@@ -460,12 +461,25 @@ workTreeItems' (AllowHidden allowhidden) ww ps = case ww of
 	
 	exists p = isJust <$> liftIO (catchMaybeIO $ getSymbolicLinkStatus p)
 
-	viasymlink Nothing = return False
-	viasymlink (Just p) =
-		ifM (liftIO $ isSymbolicLink <$> getSymbolicLinkStatus p)
-			( return True
-			, viasymlink (upFrom p)
-			)
+	prepviasymlink = do
+		repotopst <- inRepo $ 
+			maybe
+				(pure Nothing)
+				(catchMaybeIO . R.getSymbolicLinkStatus) 
+			. Git.repoWorkTree
+		return $ \st -> case repotopst of
+			Nothing -> False
+			Just tst -> fileID st == fileID tst
+				&& deviceID st == deviceID tst
+
+	viasymlink _ Nothing = return False
+	viasymlink stopattop (Just p) = do
+		st <- liftIO $ getSymbolicLinkStatus p
+		if stopattop st
+			then return False
+			else if isSymbolicLink st
+				then return True
+				else viasymlink stopattop (upFrom p)
 
 	hidden currbranch f
 		| allowhidden = isJust

doc/bugs/__39__Beyond_symbolic__39___link_error_when_link_is_upstream_of_repo.mdwn

@@ -77,3 +77,5 @@ caller's side, but since it looks like an unintended consequence of
 
 [[!meta author=kyle]]
 [[!tag projects/datalad]]
+
+> [[fixed|done]] --[[Joey]]

doc/bugs/__39__Beyond_symbolic__39___link_error_when_link_is_upstream_of_repo/comment_3_9ac6e3436ab4866993ebf4e469b13636._comment

@@ -0,0 +1,12 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 3"""
+ date="2020-08-06T22:29:49Z"
+ content="""
+AFAICS, git does something like cache the stat of the directory at the top
+of the working tree, and uses that to know which part to check for symlinks. 
+There's a lstat cache in the relevant code anyway.
+
+Ok, implemented it that way in git-annex, which I was able to do w/o doing
+any more work per file than comparing a dev and an inode.
+"""]]