Add ability to reset estimated time through the `remove_estimation` command.

app/services/slash_commands/interpret_service.rb

@@ -275,6 +275,15 @@ module SlashCommands
       end
     end
 
+    desc 'Remove the estimated time'
+    condition do
+      issuable.persisted? &&
+        current_user.can?(:"admin_#{issuable.to_ability_name}", project)
+    end
+    command :remove_estimation do
+      @updates[:time_estimate] = 0
+    end
+
     def find_label_ids(labels_param)
       label_ids_by_reference = extract_references(labels_param, :label).map(&:id)
       labels_ids_by_name = LabelsFinder.new(current_user, project_id: project.id, name: labels_param.split).execute.select(:id)

app/services/system_note_service.rb

@@ -126,7 +126,11 @@ module SystemNoteService
 
   def change_time_estimate(noteable, project, author)
     parsed_time = ChronicDuration.output(noteable.time_estimate, format: :short)
-    body = "Changed time estimate of this #{noteable.human_class_name} to #{parsed_time}"
+    body = if parsed_time
+             "Changed time estimate of this #{noteable.human_class_name} to #{parsed_time}"
+           else
+             "Removed time estimate on this #{noteable.human_class_name}"
+           end
 
     create_note(noteable: noteable, project: project, author: author, note: body)
   end

doc/user/project/slash_commands.md

@@ -30,4 +30,5 @@ do.
 | `/remove_due_date`         | Remove due date |
 | `/wip`                     | Toggle the Work In Progress status |
 | <code>/estimate &lt;1w 3d 2h 14m&gt;</code> | Set time estimate |
+| `/remove_estimation`       | Remove estimated time |
 | <code>/spend &lt;1h 30m &#124; -1h 5m&gt;</code> | Add or substract spent time |

spec/services/slash_commands/interpret_service_spec.rb

@@ -226,6 +226,14 @@ describe SlashCommands::InterpretService, services: true do
       end
     end
 
+    shared_examples 'remove_estimation command' do
+      it 'populates time_estimate: "0" if content contains /remove_estimation' do
+        _, updates = service.execute(content, issuable)
+
+        expect(updates).to eq(time_estimate: 0)
+      end
+    end
+
     shared_examples 'empty command' do
       it 'populates {} if content contains an unsupported command' do
         _, updates = service.execute(content, issuable)
@@ -497,6 +505,11 @@ describe SlashCommands::InterpretService, services: true do
       let(:issuable) { issue }
     end
 
+    it_behaves_like 'remove_estimation command' do
+      let(:content) { '/remove_estimation' }
+      let(:issuable) { issue }
+    end
+
     context 'when current_user cannot :admin_issue' do
       let(:visitor) { create(:user) }
       let(:issue) { create(:issue, project: project, author: visitor) }