main() is one call into internal/cli (closes #160)

cmd/netwatch-server/main.go parsed the command line, ran the check-cidr
and prepare-data-dir subcommands and built the fx application itself;
the Go style guide puts all of that in internal/ or pkg/. The new
package internal/cli does it, with the same arguments, messages and
exit codes. main() is now os.Exit(cli.Main(os.Stderr, Appname, Version,
os.Args[1:], cli.RunServer)): Main takes the writer for errors and the
function that runs the server, so its tests give it a buffer and a
function that fails them. Appname and Version stay in main, where the
build sets Version. The function behind prepare-data-dir also takes the
volume and the user's name, so its own tests give it a temporary
directory and the user they run as.

Model: opus-5-5

internal/reportbuf/reportbuf_test.go

@@ -334,9 +334,9 @@ func stopWhileHeld(
 	return <-stopped
 }
 
-// startApp starts a Buffer through fx, as main does, with the DATA_DIR
-// and DATA_DIR_MAX_BYTES the calling test has set, and returns it with
-// the app, for tests that stop the app themselves.
+// startApp starts a Buffer through fx, as cli.RunServer does, with the
+// DATA_DIR and DATA_DIR_MAX_BYTES the calling test has set, and returns
+// it with the app, for tests that stop the app themselves.
 func startApp(t *testing.T) (*reportbuf.Buffer, *fxtest.App) {
 	t.Helper()
 
@@ -358,8 +358,8 @@ func startApp(t *testing.T) (*reportbuf.Buffer, *fxtest.App) {
 	return buf, app
 }
 
-// startBuffer starts a Buffer through fx, as main does, with the
-// DATA_DIR and DATA_DIR_MAX_BYTES the calling test has set.
+// startBuffer starts a Buffer through fx, as cli.RunServer does, with
+// the DATA_DIR and DATA_DIR_MAX_BYTES the calling test has set.
 func startBuffer(t *testing.T) *reportbuf.Buffer {
 	t.Helper()
 
@@ -1120,8 +1120,8 @@ func TestHealthCheckFailsWhileWritesFail(t *testing.T) {
 }
 
 // startBufferWithHandlers starts a Buffer and the Handlers that store
-// reports in it through fx, as main does, with the DATA_DIR the calling
-// test has set.
+// reports in it through fx, as cli.RunServer does, with the DATA_DIR
+// the calling test has set.
 func startBufferWithHandlers(
 	t *testing.T,
 ) (*reportbuf.Buffer, *handlers.Handlers) {