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

Delete tag via API

### What does this MR do?

Implements deleting a tag via the API.

### Are there points in the code the reviewer needs to double check?

On success, it returns the name of the deleted tag. This is similar to the [delete branch API](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/api/branches.rb#L111).

###  What are the relevant issue numbers / Feature requests?

* This MR closes #1575 
* Closes http://feedback.gitlab.com/forums/176466-general/suggestions/6599203-delete-tags-through-the-api

@stanhu Could you do a review?

See merge request !1862

1 files changed, 20 insertions, 0 deletions

diff --git a/doc/api/tags.md b/doc/api/tags.md
index 085d387e824..17d12e9cc62 100644
--- a/doc/api/tags.md
+++ b/doc/api/tags.md
@@ -83,6 +83,26 @@ it will contain the annotation.
 It returns 200 if the operation succeed. In case of an error,
 405 with an explaining error message is returned.
 
+## Delete a tag
+
+Deletes a tag of a repository with given name. On success, this API method
+returns 200 with the name of the deleted tag. If the tag does not exist, the
+API returns 404.
+
+```
+DELETE /projects/:id/repository/tags/:tag_name
+```
+
+Parameters:
+
+- `id` (required) - The ID of a project
+- `tag_name` (required) - The name of a tag
+
+```json
+{
+  "tag_name": "v4.3.0"
+}
+```
 
 ## Create a new release