GIT_ANNEX_SHELL_APPENDONLY

Makes it allow writes, but not deletion of annexed content. Note that
securing pushes to the git repository is left up to the user.

This commit was sponsored by Jack Hill on Patreon.

CmdLine/GitAnnexShell/Checks.hs

@@ -26,6 +26,12 @@ readOnlyEnv = "GIT_ANNEX_SHELL_READONLY"
 checkNotReadOnly :: IO ()
 checkNotReadOnly = checkEnv readOnlyEnv
 
+appendOnlyEnv :: String
+appendOnlyEnv = "GIT_ANNEX_SHELL_APPENDONLY"
+
+checkNotAppendOnly :: IO ()
+checkNotAppendOnly = checkEnv appendOnlyEnv
+
 checkEnv :: String -> IO ()
 checkEnv var = checkEnvSet var >>= \case
 	False -> noop