gitRemoteSetOriginAction: Use regex capture group

Finally figured out how to get a capture group out of the regex match.
Needed to coerce as a two-dimensional `String` list.

Thanks to:
- https://stackoverflow.com/questions/24699279/cant-capture-a-group-in-a-string
- https://stackoverflow.com/questions/6729158/find-all-capturing-groups-of-a-regular-expression

Get the captured group and set it to the URL to insert into the
database. It lives in the second element of the first list:

    Prelude Text.Regex.TDFA> "git remote set origin https://example.new" =~ "^git remote set origin ([^ ]+)$" :: [[String]]
    [["git remote set origin https://example.new","https://example.new"]]
    Prelude Text.Regex.TDFA> "" =~ "^git remote set origin ([^ ]+)$" :: [[String]]
    []

1 files changed, 5 insertions, 3 deletions

diff --git a/src/Plugin/GitRemoteSetOrigin.hs b/src/Plugin/GitRemoteSetOrigin.hs
index 0e8f817..8cf2e51 100644
--- a/src/Plugin/GitRemoteSetOrigin.hs
+++ b/src/Plugin/GitRemoteSetOrigin.hs
@@ -20,9 +20,11 @@ gitRemoteSetOrigin = Plugin
 
 gitRemoteSetOriginAction :: PluginAction
 gitRemoteSetOriginAction message = do
-    case M.textStr message =~ matchRegex gitRemoteSetOrigin of
-        ""  -> return $ Left "blast"
-        url -> do
+    case M.textStr message =~ matchRegex gitRemoteSetOrigin :: [[String]] of
+        []    -> return $ Left "blast"
+        (m:_) -> do
+            let url = last m
+
             dbConn <- liftIO $ open "db/sorbot_development.sqlite3"
             liftIO $ execute dbConn "INSERT INTO \
                 \ plugin_github_commit_channel_repo_urls \