Added GIT_ANNEX_VECTOR_CLOCK environment variable

Can be used to override the default timestamps used in log files in the
git-annex branch. This is a dangerous environment variable; use with
caution.

Note that this only affects writing to the logs on the git-annex branch.
It is not used for metadata in git commits (other env vars can be set for
that).

There are many other places where timestamps are still used, that don't
get committed to git, but do touch disk. Including regular timestamps
of files, and timestamps embedded in some files in .git/annex/, including
the last fsck timestamp and timestamps in transfer log files.

A good way to find such things in git-annex is to get for getPOSIXTime and
getCurrentTime, although some of the results are of course false positives
that never hit disk (unless git-annex gets swapped out..)

So this commit does NOT necessarily make git-annex comply with some HIPPA
privacy regulations; it's up to the user to determine if they can use it in
a way compliant with such regulations.

Benchmarking: It takes 0.00114 milliseconds to call getEnv
"GIT_ANNEX_VECTOR_CLOCK" when that env var is not set. So, 100 thousand log
files can be written with an added overhead of only 0.114 seconds. That
should be by far swamped by the actual overhead of writing the log files
and making the commit containing them.

This commit was supported by the NSF-funded DataLad project.

1 files changed, 7 insertions, 6 deletions

diff --git a/Logs/UUIDBased.hs b/Logs/UUIDBased.hs
index 97ecd1011..fd1cd7c2d 100644
--- a/Logs/UUIDBased.hs
+++ b/Logs/UUIDBased.hs
@@ -17,7 +17,8 @@
 module Logs.UUIDBased (
 	Log,
 	LogEntry(..),
-	TimeStamp(..),
+	VectorClock,
+	currentVectorClock,
 	parseLog,
 	parseLogNew,
 	parseLogWithUUID,
@@ -29,10 +30,10 @@ module Logs.UUIDBased (
 ) where
 
 import qualified Data.Map as M
-import Data.Time.Clock.POSIX
 
 import Common
 import Types.UUID
+import Annex.VectorClock
 import Logs.MapLog
 import Logs.TimeStamp
 import Logs.Line
@@ -42,8 +43,8 @@ type Log v = MapLog UUID v
 showLog :: (v -> String) -> Log v -> String
 showLog shower = unlines . map showpair . M.toList
   where
-	showpair (k, LogEntry (Date p) v) =
-		unwords [fromUUID k, shower v, tskey ++ show p]
+	showpair (k, LogEntry (VectorClock c) v) =
+		unwords [fromUUID k, shower v, tskey ++ show c]
 	showpair (k, LogEntry Unknown v) =
 		unwords [fromUUID k, shower v]
 
@@ -75,7 +76,7 @@ parseLogWithUUID parser = M.fromListWith best . mapMaybe parse . splitLines
 			| otherwise = drop 1 $ beginning ws
 		pdate s = case parsePOSIXTime s of
 			Nothing -> Unknown
-			Just d -> Date d
+			Just d -> VectorClock d
 
 showLogNew :: (v -> String) -> Log v -> String
 showLogNew = showMapLog fromUUID
@@ -83,7 +84,7 @@ showLogNew = showMapLog fromUUID
 parseLogNew :: (String -> Maybe v) -> String -> Log v
 parseLogNew = parseMapLog (Just . toUUID)
 
-changeLog :: POSIXTime -> UUID -> v -> Log v -> Log v
+changeLog :: VectorClock -> UUID -> v -> Log v -> Log v
 changeLog = changeMapLog
 
 addLog :: UUID -> LogEntry v -> Log v -> Log v