Expose the target commit ID through the tag API

changelogs/unreleased/feature-add_target_to_tags.yml

+---
+title: Expose the target commit ID through the tag API
+merge_request:
+author:
+type: added

doc/api/tags.md

@@ -42,6 +42,7 @@ Parameters:
       "description": "Amazing release. Wow"
     },
     "name": "v1.0.0",
+    "target": "2695effb5807a22ff3d138d593fd856244e155e7",
     "message": null
   }
 ]
@@ -73,6 +74,7 @@ Example Response:
 {
   "name": "v5.0.0",
   "message": null,
+  "target": "60a8ff033665e1207714d6670fcd7b65304ec02f",
   "commit": {
     "id": "60a8ff033665e1207714d6670fcd7b65304ec02f",
     "short_id": "60a8ff03",
@@ -132,12 +134,16 @@ Parameters:
     "description": "Amazing release. Wow"
   },
   "name": "v1.0.0",
+  "target: "2695effb5807a22ff3d138d593fd856244e155e7",
   "message": null
 }
 ```
 The message will be `null` when creating a lightweight tag otherwise
 it will contain the annotation.
 
+The target will contain the tag objects ID when creating annotated tags,
+otherwise it will contain the commit ID when creating lightweight tags.
+
 In case of an error,
 status code `405` with an explaining error message is returned.
 

lib/api/entities.rb

@@ -928,7 +928,7 @@ module API
     end
 
     class Tag < Grape::Entity
-      expose :name, :message
+      expose :name, :message, :target
 
       expose :commit, using: Entities::Commit do |repo_tag, options|
         options[:project].repository.commit(repo_tag.dereferenced_target)

spec/fixtures/api/schemas/public_api/v4/tag.json

@@ -10,6 +10,7 @@
     "name": { "type": "string" },
     "message": { "type": ["string", "null"] },
     "commit": { "$ref": "commit/basic.json" },
+    "target": { "type": "string" },
     "release": {
       "oneOf": [
         { "type": "null" },