Use "matching" as keyword for regex argument of "flush"

Changelog: Change "flush" command to take regex argument via "matching" keyword

2 files changed, 4 insertions, 3 deletions

diff --git a/README.md b/README.md
index 0cf5f21..f189df0 100644
--- a/README.md
+++ b/README.md
@@ -248,10 +248,11 @@ In that case the expect command has to have the `capture` clause with matching n
 Results of the captures are then assigned to the newly created variables as strings.
 
 ```
-flush [from <proc>]
+flush [from <proc>] [matching <regex>]
 ```
 
 Flush memory of `<proc>` output, so no following `expect` command will match anything produced up to this point.
+If the `matching` clause is used, discard only output lines matching `<regex>`.
 
 ```
 guard <expr>
diff --git a/src/Test/Builtins.hs b/src/Test/Builtins.hs
index 6c6c2f0..9babb9e 100644
--- a/src/Test/Builtins.hs
+++ b/src/Test/Builtins.hs
@@ -37,11 +37,11 @@ builtinSend = SomeVarValue (FunctionArguments $ M.fromList atypes) $
 
 builtinFlush :: SomeVarValue
 builtinFlush = SomeVarValue (FunctionArguments $ M.fromList atypes) $
-    \_ args -> TestBlock [ Flush (getArg args (Just "from")) (getArgMb args Nothing) ]
+    \_ args -> TestBlock [ Flush (getArg args (Just "from")) (getArgMb args (Just "matching")) ]
   where
     atypes =
         [ ( Just "from", SomeArgumentType (ContextDefault @Process) )
-        , ( Nothing, SomeArgumentType (OptionalArgument @Regex) )
+        , ( Just "matching", SomeArgumentType (OptionalArgument @Regex) )
         ]
 
 builtinGuard :: SomeVarValue