Bound a consumer's identity by the provision it requires (hq issue 263)

The one global 20-character bound made every consumer pay an object
store's key length, even for provisions that keep no name, and a single
overflow refused the provider's whole declaration. An offer now states
its own bound (identity: {max, in} or false); unsaid, a provider told its
consumers keeps 20 and one told nothing keeps none. module check judges
every identity on the longest machine name before merge, and a provider
leaves an overflowing consumer out of its grants and composes, with the
consumer named by push, plan and status (ADR 0225).

cmd/mesh-controller/modules.go

@@ -59,8 +59,19 @@ func moduleCommand(ctx context.Context, args []string) error {
 	// `check` needs no mesh, and must not: it is what somebody runs in their own repository before
 	// there is a mesh in reach (novox/hq issue 148). A directory expands to every manifest under it.
 	if args[0] == "check" {
+		set := flag.NewFlagSet("module check", flag.ContinueOnError)
+		// The longest machine name an identity must fit on (novox/hq ADR 0225): a mesh passes its own.
+		longest := set.Int("longest-machine-name", catalogue.DefaultLongestMachine,
+			"judge each module's identity on a machine name this many characters long")
+		given, err := parseAround(set, args[1:])
+		if err != nil {
+			return err
+		}
+		if *longest < 1 {
+			return errors.New("--longest-machine-name is a length, at least 1")
+		}
 		var paths []string
-		for _, a := range args[1:] {
+		for _, a := range given {
 			if info, err := os.Stat(a); err == nil && info.IsDir() {
 				under, err := manifestsUnder(a)
 				if err != nil {
@@ -71,7 +82,7 @@ func moduleCommand(ctx context.Context, args []string) error {
 			}
 			paths = append(paths, a)
 		}
-		return moduleCheck(paths, os.Stdout)
+		return moduleCheckFor(paths, *longest, os.Stdout)
 	}
 	open, err := openStores(ctx)
 	if err != nil {