DevKit updates (#4508)

.github/PULL_REQUEST_TEMPLATE.md

@@ -9,6 +9,8 @@
 -->
 I am targeting this branch, because {reason}.
 
+In case of bug fix, `3.x` **MUST** be targeted.
+
 <!--
     Specify which issues will be fixed/closed.
     Remove it if this is not related.

CONTRIBUTING.md

@@ -191,6 +191,7 @@ Here is a short table resuming on which you have to start:
 Kind of modification | Backward Compatible (BC) | Type of release | Branch to target        | Label |
 -------------------- | ------------------------ | --------------- | ----------------------- | ----- |
 Bug fixes            | Yes                      | Patch           | `3.x`   | |
+Bug fixes            | Not on legacy            | Patch           | `3.x`   | |
 Bug fixes            | No (Only if no choice)   | Major           | `master` | |
 Feature              | Yes                      | Minor           | `3.x`   | |
 Feature              | No (Only if no choice)   | Major           | `master` | |
@@ -198,8 +199,12 @@ Deprecation          | Yes (Have to)            | Minor           | `3.x`   | |
 Deprecation removal  | No (Can't be)            | Major           | `master` | |
 
 Notes:
+  * Branch `3.x` is the branch of the **latest stable** patch releases and
+  has to be used for Backward Compatible bug fixes only.
   * Branch `3.x` is the branch of the **latest stable** minor release and
-  has to be used for Backward compatible PRs.
+  has to be used for Backward compatible enhancement PRs.
+  **No bug fix will be accepted here**, except if the bug fix concerns `3.x` and **only this one**.
+  Bug fixes merged on `3.x` will be ported on other branches by fallback merging.
   * If you PR is not **Backward Compatible** but can be, it **must** be:
     * Changing a function/method signature? Prefer create a new one and deprecate the old one.
     * Code deletion? Don't. Please deprecate it instead.

README.md

@@ -12,6 +12,7 @@ The missing Symfony Admin Generator
 
 Branch | Travis | Coveralls |
 ------ | ------ | --------- |
+3.x   | [![Build Status][travis_legacy_badge]][travis_legacy_link]     | [![Coverage Status][coveralls_legacy_badge]][coveralls_legacy_link]     |
 3.x   | [![Build Status][travis_stable_badge]][travis_stable_link]     | [![Coverage Status][coveralls_stable_badge]][coveralls_stable_link]     |
 master | [![Build Status][travis_unstable_badge]][travis_unstable_link] | [![Coverage Status][coveralls_unstable_badge]][coveralls_unstable_link] |
 
@@ -30,11 +31,15 @@ If you think you found a bug or you have a feature idea to propose, feel free to
 
 This package is available under the [MIT license](LICENSE).
 
+[travis_legacy_badge]: https://travis-ci.org/sonata-project/SonataAdminBundle.svg?branch=3.x
+[travis_legacy_link]: https://travis-ci.org/sonata-project/SonataAdminBundle
 [travis_stable_badge]: https://travis-ci.org/sonata-project/SonataAdminBundle.svg?branch=3.x
 [travis_stable_link]: https://travis-ci.org/sonata-project/SonataAdminBundle
 [travis_unstable_badge]: https://travis-ci.org/sonata-project/SonataAdminBundle.svg?branch=master
 [travis_unstable_link]: https://travis-ci.org/sonata-project/SonataAdminBundle
 
+[coveralls_legacy_badge]: https://coveralls.io/repos/github/sonata-project/SonataAdminBundle/badge.svg?branch=3.x
+[coveralls_legacy_link]: https://coveralls.io/github/sonata-project/SonataAdminBundle?branch=3.x
 [coveralls_stable_badge]: https://coveralls.io/repos/github/sonata-project/SonataAdminBundle/badge.svg?branch=3.x
 [coveralls_stable_link]: https://coveralls.io/github/sonata-project/SonataAdminBundle?branch=3.x
 [coveralls_unstable_badge]: https://coveralls.io/repos/github/sonata-project/SonataAdminBundle/badge.svg?branch=master