one-way escaping of newlines in uuid.log

A repository can have a newline in its description due to being in a
directory containing a newline, or due to git-annex describe being
passed a string with a newline in it for some reason. Putting that
newline in uuid.log breaks its format.

So, escape the newline when it enters uuid.log, to \n

This is a one-way escaping, it is not converted back to a newline
when reading the log. If it were, commands like git-annex info and
whereis would display a multi-line description, which could be confusing
to read.

And, implementing roundtripping would necessarily cause problems if an
old version of git-annex were used to set a description that contained
whatever special character is used to escape the \n. Eg, a \ or if
it used the ! prefix before base64 data that is used in some other logs,
the ! character. Then the description set by the old git-annex would not
roundtrip.

There just doesn't seem to be any benefit of roundtripping newlines through,
so why bother? And, git often displays \n for newline when a filename
contains a newline, so git-annex doing it in this case seems sorta ok
by analogy to git.

(Some other git-annex logs can also have newlines put into them if the
user really wants to break git-annex. For example:
git-annex config annex.largefiles "foo
bar"
The full list is probably config.log, remote.log, group.log,
preferred-content.log, required-content.log,
group-preferred-content.log, schedule.log. Probably there is no
good reason to use a newline in any of these, and the breakage is
probably limited to the bad data the user put in not coming back out.
And users can write any garbage to log files themselves manually in any
case. So, I am not going to address all of those at this time. If a
problem such as this one with the newline in the repository path comes
up, it can be dealt with on a case by case basis.)

Sponsored-by: Dartmouth College's Datalad project

CHANGELOG

@@ -12,6 +12,7 @@ git-annex (10.20230228) UNRELEASED; urgency=medium
     whose kernels are too old to support kernels used by the current arm64
     build.
   * importfeed: Display feed title.
+  * init: Support being ran in a repository that has a newline in its path.
 
  -- Joey Hess <id@joeyh.name>  Mon, 27 Feb 2023 12:31:14 -0400
 

Logs/UUID.hs

@@ -2,11 +2,13 @@
  -
  - uuid.log stores a list of known uuids, and their descriptions.
  -
- - Copyright 2010-2019 Joey Hess <id@joeyh.name>
+ - Copyright 2010-2023 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
+{-# LANGUAGE OverloadedStrings #-}
+
 module Logs.UUID (
 	uuidLog,
 	describeUUID,
@@ -25,15 +27,24 @@ import Logs.UUIDBased
 import qualified Annex.UUID
 
 import qualified Data.Map.Strict as M
+import qualified Data.ByteString as B
 import qualified Data.ByteString.Lazy as L
 import qualified Data.Attoparsec.ByteString.Lazy as A
+import Data.ByteString.Builder
+import Data.Char
 
 {- Records a description for a uuid in the log. -}
 describeUUID :: UUID -> UUIDDesc -> Annex ()
 describeUUID uuid desc = do
 	c <- currentVectorClock
 	Annex.Branch.change (Annex.Branch.RegardingUUID [uuid]) uuidLog $
-		buildLogOld buildUUIDDesc . changeLog c uuid desc . parseUUIDLog
+		buildLogOld builder . changeLog c uuid desc . parseUUIDLog
+  where
+	builder (UUIDDesc b) = byteString (escnewline b)
+	-- Escape any newline in the description, since newlines cannot
+	-- be present in the logged value. This is a one-way escaping.
+	escnewline = B.intercalate "\\n" . B.split newline
+	newline = fromIntegral (ord '\n')
 
 {- The map is cached for speed. -}
 uuidDescMap :: Annex UUIDDescMap

Types/UUID.hs

@@ -82,9 +82,6 @@ fromUUIDDesc (UUIDDesc d) = decodeBS d
 toUUIDDesc :: String -> UUIDDesc
 toUUIDDesc = UUIDDesc . encodeBS
 
-buildUUIDDesc :: UUIDDesc -> Builder
-buildUUIDDesc (UUIDDesc b) = byteString b
-
 type UUIDDescMap = M.Map UUID UUIDDesc
 
 instance Proto.Serializable UUID where

doc/bugs/init_fails_in_a_folder_with_newline_in_its_name.mdwn

@@ -32,3 +32,5 @@ git-annex version: 10.20230214+git26-g8f2829e646-1~ndall+1
 as `git` doesn't mind, and now annex batched commands support `-z` already for filenames with newlines in them, I think git-annex should tolerate repository folders with newlines in them too.
 
 [[!tag projects/datalad]]
+
+> [[fixed|done]] --[[Joey]]

doc/bugs/init_fails_in_a_folder_with_newline_in_its_name/comment_1_2690ed9441685068c291a182d39c2616._comment

@@ -14,10 +14,4 @@ written to uuid.log contains a newline, which prevents parsing that line of
 the log correctly. This can also be seen by passing a value
 with a newline to `git-annex describe`. It would also happen in the
 case with the newline directory if it didn't fail earlier.
-
-Another log file that has a similar problem BTW is config.log,
-which can get a newline in a value with eg
-`git annex config --set annex.largefiles "xxx\nyyy"`
-and the result is that reading the value back out omits
-the part after the newline.
 """]]