feat(core): Introduce new CLI: enola info digest

docs/use/fetch/index.md

@@ -195,6 +195,8 @@ $ ./enola fetch --http-scheme "https://www.vorburger.ch/hello.md?integrity=z8Vsn
 ...
 ```
 
+[`enola info digest`](../info/index.md#digest) is an alternative for obtaining the `?integrity=...` value.
+
 Note that while [Multihash](https://www.multiformats.io/multihash/) defines codes for [various hash functions](https://github.com/multiformats/multicodec/blob/master/table.csv),
 Enola (currently) [intentionally](https://github.com/google/guava/issues/5990#issuecomment-2571350434) only actually supports `sha2-256` & `sha2-512`.
 

docs/use/info/index.md

@@ -66,7 +66,7 @@ $ ./enola info detect "picasso.thing.yaml?mediaType=application/json"
 ...
 ```
 
-[`fetch`](../fetch/index.md) is another command to "get the bytes at" an URL.
+BTW: [`fetch`](../fetch/index.md) is the command to "get the bytes at" an URL.
 
 ## Metadata
 
@@ -77,6 +77,22 @@ $ ./enola info metadata --load=test/metadata-label-property.ttl https://example.
 
 [Metadata](../../concepts/metadata.md) explains what this is about.
 
+## Digest
+
+```bash cd ../.././..
+$ ./enola info digest --help
+...
+```
+
+So for example:
+
+```bash cd ../.././..
+$ ./enola info digest --http-scheme https://www.google.com
+...
+```
+
+This _digest_ can be used e.g. in [`?integrity=...` of `fetch`](../fetch/index.md#integrity).
+
 ## Screencast
 
 ![Demo](script.svg)

java/dev/enola/cli/BUILD

@@ -29,6 +29,8 @@ java_binary(
     ),
     main_class = "dev.enola.cli.EnolaCLI",
     deps = [
+        "@enola_maven//:com_github_multiformats_java_multibase",
+        "@enola_maven//:com_github_multiformats_java_multihash",
         "//java/dev/enola",
         # TODO Remove most of these direct deps, through new Enola API...
         "//java/dev/enola/common",

java/dev/enola/cli/DetectCommand.java

@@ -38,13 +38,13 @@ public class DetectCommand extends CommandWithResourceProvider {
 
     @Spec CommandSpec spec;
 
-    @CommandLine.Parameters(index = "0", paramLabel = "iri", description = "IRI")
-    String iri;
+    @CommandLine.Parameters(index = "0", paramLabel = "url", description = "URL")
+    String url;
 
     @Override
     public Integer call() throws Exception {
         super.run();
-        var uri = URIs.parse(iri);
+        var uri = URIs.parse(url);
         try (var ctx = TLC.open().push(URIs.ContextKeys.BASE, Paths.get("").toUri())) {
             var resource = rp.getResource(uri);
             if (resource == null) {

java/dev/enola/cli/DigestCommand.java

@@ -0,0 +1,59 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright 2025 The Enola <https://enola.dev> Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package dev.enola.cli;
+
+import dev.enola.common.context.TLC;
+import dev.enola.common.io.hashbrown.Multihashes;
+import dev.enola.common.io.hashbrown.ResourceHasher;
+import dev.enola.common.io.iri.URIs;
+
+import io.ipfs.multibase.Multibase;
+import io.ipfs.multihash.Multihash;
+
+import picocli.CommandLine;
+
+import java.nio.file.Paths;
+
+@CommandLine.Command(
+        name = "digest",
+        description =
+                "Generates a Message Authentication Code (MAC; also Message Integrity Code, MIC)"
+                        + " for a given URL.\n"
+                        + "See also the related ?integrity=... argument of the 'fetch' command.")
+public class DigestCommand extends CommandWithResourceProvider {
+
+    @CommandLine.Spec CommandLine.Model.CommandSpec spec;
+
+    @CommandLine.Parameters(index = "0", paramLabel = "url", description = "URL")
+    String url;
+
+    @Override
+    public Integer call() throws Exception {
+        super.run();
+        var pw = spec.commandLine().getOut();
+
+        var uri = URIs.parse(url);
+        try (var ctx = TLC.open().push(URIs.ContextKeys.BASE, Paths.get("").toUri())) {
+            var resource = rp.getResource(uri);
+
+            var multihash = new ResourceHasher().hash(resource, Multihash.Type.sha2_512);
+            pw.println(Multihashes.toString(multihash, Multibase.Base.Base64));
+        }
+        return 0;
+    }
+}

java/dev/enola/cli/InfoCommand.java

@@ -23,9 +23,10 @@
         name = "info",
         description = "Provides various information",
         subcommands = {
+            MetadataCommand.class,
             ExtensionsInfoCommand.class,
             MediaTypeInfoCommand.class,
             DetectCommand.class,
-            MetadataCommand.class
+            DigestCommand.class
         })
 public class InfoCommand {}