Add --sync flag for one-shot sync-and-exit mode

Useful for wake-from-sleep hooks: run 'converge --sync' to commit
any pending changes, pull from remotes, and push, then exit.
Shows 'Syncing N repo(s)' instead of 'Watching N repo(s)'.

app/Main.hs

@@ -22,6 +22,8 @@ data CliArgs = CliArgs
     -- ^ Log level override.
     , cliLogFile :: !(Maybe FilePath)
     -- ^ Log file path.
+    , cliSync :: !Bool
+    -- ^ Run a single sync cycle and exit (useful for wake-from-sleep hooks).
     }
 
 cliParser :: Parser CliArgs
@@ -87,6 +89,11 @@ cliParser =
                     <> help "Write logs to a file instead of stderr"
                 )
             )
+        <*> switch
+            ( long "sync"
+                <> short 's'
+                <> help "Run a single sync cycle (commit + pull + push) and exit"
+            )
 
 parserInfo :: ParserInfo CliArgs
 parserInfo =
@@ -134,15 +141,26 @@ main = do
             hPutStrLn stderr ("Using config: " <> path)
         Nothing ->
             hPutStrLn stderr "No config file found, using single-repo mode"
-    hPutStrLn stderr $
-        "Watching "
-            <> show (length (optRepos options))
-            <> " repo(s)"
-            <> " (debounce: "
-            <> show (optDebounceMs options)
-            <> "ms)"
-    mapM_ (\r -> hPutStrLn stderr ("  - " <> rcPath r)) (optRepos options)
-    runConverge options
+    let repos = optRepos options
+    if cliSync cli
+        then do
+            hPutStrLn stderr $
+                "Syncing "
+                    <> show (length repos)
+                    <> " repo(s)"
+            mapM_ (\r -> hPutStrLn stderr ("  - " <> rcPath r)) repos
+            logger <- newLogger (optLogLevel options) (optLogFile options)
+            mapM_ (syncRepo options logger) repos
+        else do
+            hPutStrLn stderr $
+                "Watching "
+                    <> show (length repos)
+                    <> " repo(s)"
+                    <> " (debounce: "
+                    <> show (optDebounceMs options)
+                    <> "ms)"
+            mapM_ (\r -> hPutStrLn stderr ("  - " <> rcPath r)) repos
+            runConverge options
 
 
 -- | Apply CLI overrides (debounce, log level, log file) to Options.