Issue 332: add unlink-dangling and the glob refusal from the review

disable cannot remove a link whose unit file is gone, so the verb that
finds it needed one that removes it.

04-ISSUES/332-the-service-manager-cannot-clear-or-explain-a-failed-unit/00-report.md

@@ -41,21 +41,35 @@ Two verbs on the seat, each saying the command it replaces:
   it points, whether it dangles and whose directory it is in. It replaces `systemctl list-dependencies
   --reverse` and reading the `*.wants` directories by hand.
 
+A third verb followed from the review of the first two. `systemctl disable` does not remove an enable
+link once the unit's file is gone, so the link found by `wanted-by` had no verb to remove it either:
+
+- **`unlink-dangling {unit, scope, why}`** removes the dangling enable links named for one unit, only in
+  the account's or the machine's own configuration, on the person's word. It never removes a package's, a
+  generator's or the runtime's link, and leaves any link that changed since it was read. Each link is
+  recorded with its target and the reason before it is removed.
+
+The review also made every verb refuse a unit name holding `*`, `?` or `[`: the service manager expands a
+glob to every unit it matches, so `reset-failed` or `stop` of `*` would have acted on all of them.
+
 They land in the three steps of
 [ADR 0246](../../02-DECISIONS/0246-a-seats-new-verb-is-promised-before-it-is-required.md):
 
-1. The controller promises both verbs as optional (mesh-controller, this issue's first pull request).
-2. The `systemd` module serves both (mesh-catalog). Its check passes only against a controller that
-   already promises them, so it merges after step 1 is delivered.
-3. The controller requires both, in a later pull request, once every holder serves them.
+1. The controller promises the verbs as optional: mesh-controller #158 (`reset-failed`, `wanted-by`) and
+   #160 (`unlink-dangling`).
+2. The `systemd` module serves them: mesh-catalog #137 and #138. A module's check passes only against a
+   controller that already promises its verbs, so each merges after its step 1 is delivered.
+3. The controller requires them, in a later pull request, once every holder serves them.
 
 ## How it is checked
 
-- mesh-controller: `TestResetFailedAndWantedByAreOptionalVerbsOfTheServiceManager` (both promised,
-  optional, read back optional from the store's row, each naming the command it replaces), and the seat's
-  verb list in `TestTheServiceManagerSeatServesTheUnitVerbs`.
+- mesh-controller: `TestResetFailedAndWantedByAreOptionalVerbsOfTheServiceManager` (the verbs promised,
+  optional, read back optional from the store's row, each naming the command it replaces, and `why`
+  required of `unlink-dangling`), and the seat's verb list in `TestTheServiceManagerSeatServesTheUnitVerbs`.
 - mesh-catalog `modules/systemd`: the `wanted_test.go` tests (a dangling enable link in the account's own
   configuration found and named, a link matched by its target, an unreadable directory and an unreachable
   manager said rather than read as nothing, read-only), and the manifest test that the module serves exactly
-  the verbs it claims.
+  the verbs it claims. `TestAGlobIsRefusedAsAUnitByEveryVerb` covers every verb taking a unit. The
+  `unlink_test.go` tests check what is removed and what is left, that the record is written before each
+  removal, and that a link outside the account's home goes through `sudo -n`.
 - Step 3 is not checked by anything yet, as ADR 0246 says of every optional verb.