Merge branch 'api-dev-can-push' into 'master'

API: Expose 'developers_can_push' for branches

## What does this MR do?

Adds support for the `developers_can_push` flag for the branches API. It also supports creating protected branches with that flag.

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

The API call requires an optional boolean parameter `developers_can_push`. If it is not either `true` or `false`, it should not update the value. I'm not sure if this is the right way to do it.

Right now it always returns `200`. Maybe the `PUT` method should return different status codes depending if it really created or updated a branch.

## What are the relevant issue numbers?

Closes #12735 

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5208

1 files changed, 16 insertions, 4 deletions

diff --git a/doc/api/branches.md b/doc/api/branches.md
index abc4732c395..dbe8306c66f 100644
--- a/doc/api/branches.md
+++ b/doc/api/branches.md
@@ -23,6 +23,8 @@ Example response:
   {
     "name": "master",
     "protected": true,
+    "developers_can_push": false,
+    "developers_can_merge": false,
     "commit": {
       "author_email": "john@example.com",
       "author_name": "John Smith",
@@ -64,6 +66,8 @@ Example response:
 {
   "name": "master",
   "protected": true,
+  "developers_can_push": false,
+  "developers_can_merge": false,
   "commit": {
     "author_email": "john@example.com",
     "author_name": "John Smith",
@@ -91,13 +95,15 @@ PUT /projects/:id/repository/branches/:branch/protect
 ```
 
 ```bash
-curl -X PUT -H "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v3/projects/5/repository/branches/master/protect
+curl -X PUT -H "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v3/projects/5/repository/branches/master/protect?developers_can_push=true&developers_can_merge=true
 ```
 
 | Attribute | Type | Required | Description |
 | --------- | ---- | -------- | ----------- |
 | `id` | integer | yes | The ID of a project |
 | `branch` | string | yes | The name of the branch |
+| `developers_can_push` | boolean | no | Flag if developers can push to the branch |
+| `developers_can_merge` | boolean | no | Flag if developers can merge to the branch |
 
 Example response:
 
@@ -117,7 +123,9 @@ Example response:
     ]
   },
   "name": "master",
-  "protected": true
+  "protected": true,
+  "developers_can_push": true,
+  "developers_can_merge": true
 }
 ```
 
@@ -158,7 +166,9 @@ Example response:
     ]
   },
   "name": "master",
-  "protected": false
+  "protected": false,
+  "developers_can_push": false,
+  "developers_can_merge": false
 }
 ```
 
@@ -196,7 +206,9 @@ Example response:
     ]
   },
   "name": "newbranch",
-  "protected": false
+  "protected": false,
+  "developers_can_push": false,
+  "developers_can_merge": false
 }
 ```