fix(update): Help people discover how they pull in a stale dep

I put this behind `--verbose`
- To keep the output down in the standard case
- Because its assuming  most people's "behind" dependencies will be
  "Unchanged" and so that is when knowing how to look up how its pulled
  in is useful

Author: epage

src/cargo/ops/cargo_generate_lockfile.rs

@@ -244,17 +244,20 @@ pub fn update_lockfile(ws: &Workspace<'_>, opts: &UpdateOptions<'_>) -> CargoRes
                         &anstyle::Style::new().bold(),
                     )?;
                 }
-            } else {
-                if !unchanged.is_empty() {
-                    unchanged_behind += 1;
-                }
             }
+            unchanged_behind += unchanged.len();
         }
     }
-    if 0 < unchanged_behind {
-        opts.config.shell().note(format!(
-            "Pass `--verbose` to see {unchanged_behind} unchanged dependencies behind latest"
-        ))?;
+    if opts.config.shell().verbosity() == Verbosity::Verbose {
+        opts.config.shell().note(
+            "To see how you depend on a package, run `cargo tree --invert --package <dep>@<ver>`",
+        )?;
+    } else {
+        if 0 < unchanged_behind {
+            opts.config.shell().note(format!(
+                "Pass `--verbose` to see {unchanged_behind} unchanged dependencies behind latest"
+            ))?;
+        }
     }
     if opts.dry_run {
         opts.config

tests/testsuite/update.rs

@@ -1520,6 +1520,7 @@ fn report_behind() {
 [UPDATING] `dummy-registry` index
 [UPDATING] breaking v0.1.0 -> v0.1.1 (latest: v0.2.0)
 [UNCHANGED] pre v1.0.0-alpha.0 (latest: v1.0.0-alpha.1)
+[NOTE] To see how you depend on a package, run `cargo tree --invert --package <dep>@<ver>`
 [WARNING] not updating lockfile due to dry run
 ",
         )
@@ -1543,6 +1544,7 @@ fn report_behind() {
 [UPDATING] `dummy-registry` index
 [UNCHANGED] breaking v0.1.1 (latest: v0.2.0)
 [UNCHANGED] pre v1.0.0-alpha.0 (latest: v1.0.0-alpha.1)
+[NOTE] To see how you depend on a package, run `cargo tree --invert --package <dep>@<ver>`
 [WARNING] not updating lockfile due to dry run
 ",
         )