benchmark: Add --databases to benchmark sqlite databases

Rescued from commit 11d6e2e260 which removed
db benchmarks in favor of benchmarking arbitrary git-annex commands. Which
is nice and general, but microbenchmarks are useful too.

Command/Benchmark.hs

@@ -11,10 +11,11 @@ module Command.Benchmark where
 
 import Command
 import Types.Benchmark
-
 #ifdef WITH_BENCHMARK
+import Database.Benchmark
+
 import Criterion.Main
-import Criterion.Main.Options (parseWith, Mode)
+import Criterion.Main.Options (parseWith)
 #endif
 
 cmd :: BenchmarkGenerator -> Command
@@ -23,20 +24,26 @@ cmd generator = command "benchmark" SectionTesting
 	paramNothing
 	(seek generator <$$> optParser)
 
-#ifndef WITH_BENCHMARK
-type Mode = ()
-#endif
-
-data BenchmarkOptions = BenchmarkOptions CmdParams Mode
+data BenchmarkOptions 
+	= BenchmarkOptions CmdParams CriterionMode
+	| BenchmarkDatabases CriterionMode
 
 optParser :: CmdParamsDesc -> Parser BenchmarkOptions
-optParser desc = BenchmarkOptions
-	<$> cmdParams desc
+optParser desc = benchmarkoptions <|> benchmarkdatabases
+  where
+	benchmarkoptions = BenchmarkOptions
+		<$> cmdParams desc
+		<*> criterionopts
+	benchmarkdatabases = BenchmarkDatabases
+		<$> criterionopts
+		<* flag' () 
+			( long "databases"
+			<> help "benchmark sqlite databases"
+			)
 #ifdef WITH_BENCHMARK
-	-- parse criterion's options
-	<*> parseWith defaultConfig
+	criterionopts = parseWith defaultConfig
 #else
-	<*> pure ()
+	criterionopts = pure ()
 #endif
 
 seek :: BenchmarkGenerator -> BenchmarkOptions -> CommandSeek
@@ -44,6 +51,7 @@ seek :: BenchmarkGenerator -> BenchmarkOptions -> CommandSeek
 seek generator (BenchmarkOptions ps mode) = do
 	runner <- generator ps
 	liftIO $ runMode mode [ bench (unwords ps) $ nfIO runner ]
+seek _ (BenchmarkDatabases mode) = benchmarkDbs mode
 #else
 seek _ _ = giveup "git-annex is not built with benchmarking support"
 #endif