restoreDatabaseFromSite: populate metaBackup

This fixes the following problem:

```
$ glean create --db-root /tmp/g --db test/0 --finish
$ glean backup --db-root /tmp/g test/0 mock:/tmp/b
$ glean delete --db-root /tmp/g --db test/0
$ glean restore --db-root /tmp/g mock:/tmp/b/test.0
I20260107 10:30:07.484591 574661 Env.hs:65] Using schema from dir:/home/simon/.cabal/store/ghc-9.4.7/glean-0.2.0.0-l-db-b1c66a68faaa1c60cea64cb6e1de59f08ce55ddbe40247f16da611febd4a042d/share/glean/schema/source
I20260107 10:30:07.612099 574661 Restore.hs:197] Restoring from mock:/tmp/b/test.0
error: didE20260107 10:30:07.612265 574665 Backup.hs:324] test/0: restore: missing location
 not find database locator mock:/tmp/b/test.0
```

`doRestore` expects to find the locator in `metaBackup`, but when we
restore a database using `glean restore`, the entry point is
`restoreDatabaseFromSite`, which gets the `Meta` from `Backup.inspect`,
which may not populate `metaBackup`. Furthermore it would be hard for
`Backup.inspect` to populate this field because it would have to
reconstruct the backup locator, which `restoreDatabaseFromSite` already
has.

So we just populate `metaBackup` in `restoreDatabaseFromSite`.

Author: simonmar

glean/db/Glean/Database/Restore.hs

@@ -13,13 +13,15 @@ module Glean.Database.Restore (
 ) where
 
 import Control.Exception hiding(handle)
+import Data.Maybe
 import qualified Data.Set as Set
 import Data.Text (Text)
 
 import Util.STM
 
 import qualified Glean.Database.Backup.Backend as Backup
 import qualified Glean.Database.Backup.Locator as Backup
+import Glean.Database.Meta
 import qualified Glean.Database.Catalog as Catalog
 import Glean.Database.Types
 import qualified Glean.ServerConfig.Types as ServerConfig
@@ -66,7 +68,7 @@ restoreDatabase :: Env -> Text -> IO ()
 restoreDatabase env loc
   | Just (_, site, repo) <-
       Backup.fromRepoLocator (envBackupBackends env) loc =
-        atomically =<< restoreDatabaseFromSite env site repo
+        atomically =<< restoreDatabaseFromSite env site repo loc
   | otherwise = throwIO $
       Thrift.InvalidLocator $ "invalid locator '" <> loc <>  "'"
 
@@ -75,7 +77,15 @@ restoreDatabaseFromSite
   => Env
   -> site
   -> Repo
+  -> Text
   -> IO (STM ())
-restoreDatabaseFromSite Env{..} site repo = do
+restoreDatabaseFromSite Env{..} site repo loc = do
   props <- Backup.inspect site repo
-  return $ Catalog.startRestoring envCatalog repo props
+  -- doRestore expects to find the location in metaBackup, but
+  -- Backup.inspect is not required to populate this so we fill it
+  -- in if it's missing.
+  let props'
+        | isNothing (metaBackup props) =
+            props { metaBackup = Just loc }
+        | otherwise = props
+  return $ Catalog.startRestoring envCatalog repo props'