Merge branch 'api-retrieve-tag' into 'master'

API: Ability to retrieve a single tag

* Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/14330

/cc @dblessing 

See merge request !3567

4 files changed, 65 insertions, 1 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 8db9a9b0d1e..e0ae6b79751 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -22,6 +22,7 @@ v 8.7.0 (unreleased)
   - Remove "Congratulations!" tweet button on newly-created project. (Connor Shea)
   - Improved UX of the navigation sidebar
   - Build status notifications
+  - API: Ability to retrieve a specific tag (Robert Schilling)
 
 v 8.6.5 (unreleased)
   - Check permissions when user attempts to import members from another project
diff --git a/doc/api/tags.md b/doc/api/tags.md
index 17d12e9cc62..c451a42b725 100644
--- a/doc/api/tags.md
+++ b/doc/api/tags.md
@@ -38,6 +38,38 @@ Parameters:
 ]
 ```
 
+## Get a single repository tag
+
+Get a specific repository tag determined by its name. It returns 200 together
+with the tag information if the tag exists. It returns 404 if the tag does not
+exist.
+
+Parameters:
+
+- `id` (required) - The ID of a project
+- `tag_name` (required) - The name of the tag
+
+```json
+{
+  "name": "v5.0.0",
+  "message": null,
+  "commit": {
+    "id": "60a8ff033665e1207714d6670fcd7b65304ec02f",
+    "message": "v5.0.0\n",
+    "parent_ids": [
+      "f61c062ff8bcbdb00e0a1b3317a91aed6ceee06b"
+    ],
+    "authored_date": "2015-02-01T21:56:31.000+01:00",
+    "author_name": "Arthur Verschaeve",
+    "author_email": "contact@arthurverschaeve.be",
+    "committed_date": "2015-02-01T21:56:31.000+01:00",
+    "committer_name": "Arthur Verschaeve",
+    "committer_email": "contact@arthurverschaeve.be"
+  },
+  "release": null
+}
+```
+
 ## Create a new tag
 
 Creates a new tag in the repository that points to the supplied ref.
@@ -148,4 +180,4 @@ Parameters:
   "tag_name": "1.0.0",
   "description": "Amazing release. Wow"
 }
-```
\ No newline at end of file
+```
diff --git a/lib/api/tags.rb b/lib/api/tags.rb
index 2d8a9e51bb9..731a68082ba 100644
--- a/lib/api/tags.rb
+++ b/lib/api/tags.rb
@@ -16,6 +16,20 @@ module API
                 with: Entities::RepoTag, project: user_project
       end
 
+      # Get a single repository tag
+      #
+      # Parameters:
+      #   id (required) - The ID of a project
+      #   tag_name (required) - The name of the tag
+      # Example Request:
+      #   GET /projects/:id/repository/tags/:tag_name
+      get ":id/repository/tags/:tag_name", requirements: { tag_name: /.*/ } do
+        tag = user_project.repository.find_tag(params[:tag_name])
+        not_found!('Tag') unless tag
+
+        present tag,  with: Entities::RepoTag, project: user_project
+      end
+
       # Create tag
       #
       # Parameters:
diff --git a/spec/requests/api/tags_spec.rb b/spec/requests/api/tags_spec.rb
index a15be07ed57..acbd9c3e332 100644
--- a/spec/requests/api/tags_spec.rb
+++ b/spec/requests/api/tags_spec.rb
@@ -40,6 +40,23 @@ describe API::API, api: true  do
     end
   end
 
+  describe "GET /projects/:id/repository/tags/:tag_name" do
+    let(:tag_name) { project.repository.tag_names.sort.reverse.first }
+
+    it 'should return a specific tag' do
+      get api("/projects/#{project.id}/repository/tags/#{tag_name}", user)
+
+      expect(response.status).to eq(200)
+      expect(json_response['name']).to eq(tag_name)
+    end
+
+    it 'should return 404 for an invalid tag name' do
+      get api("/projects/#{project.id}/repository/tags/foobar", user)
+
+      expect(response.status).to eq(404)
+    end
+  end
+
   describe 'POST /projects/:id/repository/tags' do
     context 'lightweight tags' do
       it 'should create a new tag' do