feature #5994 Updated the release process for Symfony 3.x and future releases (javiereguiluz)

This PR was merged into the 2.3 branch.

Discussion
----------

Updated the release process for Symfony 3.x and future releases

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | -

Commits
-------

23cc779 Updated the other image too
99070c9 Fixed the image
6881e07 Minor typo
442e56a Rewords
427daab Minor changes
636d348 Updated the release process for Symfony 3.x and future releases

Author: weaverryan

contributing/community/releases.rst

@@ -1,36 +1,30 @@
 The Release Process
 ===================
 
-This document explains the Symfony release process (Symfony being the code
-hosted on the main ``symfony/symfony`` `Git repository`_).
+This document explains the **release process** of the Symfony project (i.e. the
+code hosted on the main ``symfony/symfony`` `Git repository`_).
 
-Symfony manages its releases through a *time-based model*; a new Symfony minor
-version comes out every *six months*: one in *May* and one in *November*.
+Symfony manages its releases through a *time-based model* and follows the
+`Semantic Versioning`_ strategy:
 
-.. tip::
-
-    The meaning of "minor" comes from the `Semantic Versioning`_ strategy.
-
-Each minor version sticks to the same very well-defined process where we start
-with a development period, followed by a maintenance period.
-
-.. note::
-
-    This release process has been adopted as of Symfony 2.2, and all the
-    "rules" explained in this document must be strictly followed as of Symfony
-    2.4.
+* A new Symfony minor version (e.g. 2.8, 3.2, 4.1) comes out every *six months*:
+  one in *May* and one in *November*;
+* A new Symfony major version (e.g., 3.0, 4.0) comes out every *two years* and
+  it's released at the same time of the last minor version of the previous major
+  version.
 
 .. _contributing-release-development:
 
 Development
 -----------
 
-The full development period lasts six months and is divided into two phases:
+The full development period for any major or minor version lasts six months and
+is divided into two phases:
 
-* *Development*: *Four months* to add new features and to enhance existing
+* **Development**: *Four months* to add new features and to enhance existing
   ones;
 
-* *Stabilisation*: *Two months* to fix bugs, prepare the release, and wait
+* **Stabilization**: *Two months* to fix bugs, prepare the release, and wait
   for the whole Symfony ecosystem (third-party libraries, bundles, and
   projects using Symfony) to catch up.
 
@@ -43,37 +37,48 @@ final release.
 Maintenance
 -----------
 
-Each Symfony minor version is maintained for a fixed period of time, depending
-on the type of the release. We have two maintenance periods:
+Each Symfony version is maintained for a fixed period of time, depending on the
+type of the release. This maintenance is divided into:
 
 * *Bug fixes and security fixes*: During this period, all issues can be fixed.
   The end of this period is referenced as being the *end of maintenance* of a
   release.
 
 * *Security fixes only*: During this period, only security related issues can
-  be fixed. The end of this period is referenced as being the *end of
-  life* of a release.
+  be fixed. The end of this period is referenced as being the *end of life* of
+  a release.
+
+Symfony Versions
+----------------
 
 Standard Versions
 ~~~~~~~~~~~~~~~~~
 
-A standard minor version is maintained for an *eight month* period for bug
+A **Standard Minor Version** is maintained for an *eight month* period for bug
 fixes, and for a *fourteen month* period for security issue fixes.
 
+In Symfony 2.x branch, the number of minor versions wasn't constrained, so that
+branch ended up with nine minor versions (from 2.0 to 2.8). Starting from
+3.x branch, the number of minor versions is limited to five (from X.0 to X.4).
+
 .. _releases-lts:
 
 Long Term Support Versions
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Every two years, a new Long Term Support Version (aka LTS version) is
-published. Each LTS version is supported for a *three year* period for bug
+Every two years, a new **Long Term Support Version** (usually abbreviated as "LTS")
+is published. Each LTS version is supported for a *three year* period for bug
 fixes, and for a *four year* period for security issue fixes.
 
 .. note::
 
     Paid support after the three year support provided by the community can
     also be bought from `SensioLabs`_.
 
+In Symfony 2.x branch, the LTS versions are 2.3, 2.7 and 2.8. Starting from 3.x
+branch, only the last minor version of each branch is considered LTS (e.g. 3.4,
+4.4, 5.4, etc.)
+
 Schedule
 --------
 
@@ -83,7 +88,7 @@ Below is the schedule for the first few versions that use this release model:
    :align: center
 
 * **Yellow** represents the Development phase
-* **Blue** represents the Stabilisation phase
+* **Blue** represents the Stabilization phase
 * **Green** represents the Maintenance period
 
 This results in very predictable dates and maintenance periods:
@@ -100,15 +105,23 @@ Version  Feature Freeze  Release  End of Maintenance        End of Life
 2.6      09/2014         11/2014  07/2015 (8 months)        01/2016
 **2.7**  03/2015         05/2015  05/2018 (36 months)       05/2019
 **2.8**  09/2015         11/2015  11/2018 (36 months [2]_)  11/2019
-3.0      09/2015         11/2015  07/2016 (8 months)        01/2017
+3.0      09/2015         11/2015  07/2016 (8 months) [3]_)  01/2017
 3.1      03/2016         05/2016  01/2017 (8 months)        07/2017
 3.2      09/2016         11/2016  07/2017 (8 months)        01/2018
-**3.3**  03/2017         05/2017  05/2020 (36 months)       05/2021
+3.3      03/2017         05/2017  01/2018 (8 months)        07/2018
+**3.4**  09/2017         11/2017  11/2020 (36 months)       11/2021
+4.0      09/2017         11/2017  07/2018 (8 months)        01/2019
+4.1      03/2018         05/2018  01/2019 (8 months)        07/2019
+4.2      09/2018         11/2018  07/2019 (8 months)        01/2020
+4.3      03/2019         05/2019  01/2020 (8 months)        07/2020
+**4.4**  09/2019         11/2019  11/2022 (36 months)       11/2023
+5.0      09/2019         11/2019  07/2020 (8 months)        01/2021
 ...      ...             ...      ...                       ...
 =======  ==============  =======  ========================  ===========
 
 .. [1] Symfony 2.4 maintenance has been `extended to September 2014`_.
 .. [2] Symfony 2.8 is the last version of the Symfony 2.x branch.
+.. [3] Symfony 3.0 is the first version to use the new release process based on five minor releases.
 
 .. tip::
 
@@ -133,11 +146,6 @@ of Symfony to the next one.
 Whenever keeping backward compatibility is not possible, the feature, the
 enhancement or the bug fix will be scheduled for the next major version.
 
-.. note::
-
-    The work on a new major version of Symfony starts whenever enough major
-    features breaking backward compatibility are waiting on the todo-list.
-
 Deprecations
 ------------