Support hot-swapping of removable drives containing gcrypt repositories.

To support this, a core.gcrypt-id is stored by git-annex inside the git
config of a local gcrypt repository, when setting it up.

That is compared with the remote's cached gcrypt-id. When different, a
drive has been changed. git-annex then looks up the remote config for
the uuid mapped from the core.gcrypt-id, and tweaks the configuration
appropriately. When there is no known config for the uuid, it will refuse to
use the remote.

1 files changed, 5 insertions, 2 deletions

diff --git a/Config.hs b/Config.hs
index 1e4d6caec..ac251983a 100644
--- a/Config.hs
+++ b/Config.hs
@@ -36,8 +36,11 @@ setConfig (ConfigKey key) value = do
 
 {- Unsets a git config setting. (Leaves it in state currently.) -}
 unsetConfig :: ConfigKey -> Annex ()
-unsetConfig (ConfigKey key) = inRepo $ Git.Command.run
-	[Param "config", Param "--unset", Param key]
+unsetConfig ck@(ConfigKey key) = ifM (isJust <$> getConfigMaybe ck)
+	( inRepo $ Git.Command.run
+		[Param "config", Param "--unset", Param key]
+	, noop -- avoid unsetting something not set; that would fail
+	)
 
 {- A per-remote config setting in git config. -}
 remoteConfig :: Git.Repo -> UnqualifiedConfigKey -> ConfigKey