Make master the rolling release branch (#2705)

* Change default TAG in Makefile

We are going to drop the `dev` branch. The Docker tag `dev-*` are based
on this branch and so there will be no longer be generated. We must use
images based on the `master` branch (i.e. `latest`, `alpine` and `arm`).

* Remove references to dev branch in documentation

* Synchronize French documentation

3 files changed, 11 insertions, 12 deletions

diff --git a/docs/en/developers/01_First_steps.md b/docs/en/developers/01_First_steps.md
index 6c6177aec..dd56a6af6 100644
--- a/docs/en/developers/01_First_steps.md
+++ b/docs/en/developers/01_First_steps.md
@@ -37,10 +37,10 @@ $ make stop
 
 If you're interested in the configuration, the `make` commands are defined in the [`Makefile`](/Makefile).
 
-If you need to use a different tag image (default is `dev-alpine`), you can set the `TAG` environment variable:
+If you need to use a different tag image (default is `alpine`), you can set the `TAG` environment variable:
 
 ```console
-$ TAG=dev-arm make start
+$ TAG=arm make start
 ```
 
 You can find the full list of available tags [on the Docker hub](https://hub.docker.com/r/freshrss/freshrss/tags).
@@ -50,10 +50,10 @@ If you want to build the Docker image yourself, you can use the following comman
 ```console
 $ make build
 $ # or
-$ TAG=dev-arm make build
+$ TAG=arm make build
 ```
 
-The `TAG` variable can be anything (e.g. `dev-local`). You can target a specific architecture by adding `-alpine` or `-arm` at the end of the tag (e.g. `dev-local-arm`).
+The `TAG` variable can be anything (e.g. `local`). You can target a specific architecture by adding `-alpine` or `-arm` at the end of the tag (e.g. `local-arm`).
 
 # Project architecture
 
diff --git a/docs/en/developers/02_Github.md b/docs/en/developers/02_Github.md
index a1677d2af..a898dc23e 100644
--- a/docs/en/developers/02_Github.md
+++ b/docs/en/developers/02_Github.md
@@ -88,8 +88,8 @@ git remote -v show
 
 Now you can pull the latest development code:
 ```bash
-git checkout dev
-git pull upstream dev
+git checkout master
+git pull upstream master
 ```
 
 ## Starting a new development branch
@@ -110,7 +110,7 @@ git show
 git push
 ```
 
-Now you can create a PR based on your branch. Please make sure to file it against the `dev` branch!
+Now you can create a PR based on your branch.
 
 ## How to write a commit message
 
diff --git a/docs/en/developers/05_Release_new_version.md b/docs/en/developers/05_Release_new_version.md
index d8e3026f3..0cb296d0c 100644
--- a/docs/en/developers/05_Release_new_version.md
+++ b/docs/en/developers/05_Release_new_version.md
@@ -8,14 +8,13 @@ It's also recommended to make the announcement on mailing@freshrss.org.
 
 Before releasing a new version of FreshRSS, you must ensure that the code is stable and free of major bugs. Ideally, our tests should be automated and executed before any publication.
 
-You must also **make sure that the CHANGELOG file is up to date** in the dev branch with the updates of the version(s) to be released.
+You must also **make sure that the CHANGELOG file is up to date** with the updates of the version to be released.
 
 # Git process
 
 ```bash
 $ git checkout master
 $ git pull
-$ git merge --ff dev
 $ vim constants.php
 # Update version number x.y.y.z of FRESHRSS_VERSION
 $ git commit -a
@@ -33,7 +32,7 @@ The repository managing the code is located on GitHub: [FreshRSS/update.freshrss
 
 ## Writing the update script
 
-The scripts are located in the `./scripts/` directory and must take the form `update_to_x.y.z.z.php`. This directory  also contains `update_to_dev.php` intended for updates of the dev branch (this script must not include code specific to a particular version!) and `update_util.php`, which contains a list of functions useful for all scripts.
+The scripts are located in the `./scripts/` directory and must take the form `update_to_x.y.z.z.php`. This directory  also contains `update_to_dev.php` intended for updates of the `master` branch (this script must not include code specific to a particular version!) and `update_util.php`, which contains a list of functions useful for all scripts.
 
 In order to write a new script, it's better to copy/paste the last version or to start from `update_to_dev.php`. The first thing to do is to define the URL from which the FreshRSS package will be downloaded (`PACKAGE_URL`). The URL is in the form  of `https://codeload.github.com/FreshRSS/FreshRSS/zip/x.y.z`.
 
@@ -68,7 +67,7 @@ return array(
 And here's how this table works:
 
 * on the left you can find the N version, on the right the N+1 version;
-* the `x.y.z.z-dev` versions are **all** updated to `dev`;
+* the `x.y.z.z-dev` versions are **all** updated to `master`;
 * stable versions are updated to stable versions;
 * it's possible to skip several versions at once, provided that the update scripts support it;
 * it's advisable to indicate the correspondence of the current version to its potential future version by specifying that this version does not yet exist. As long as the corresponding script does not exist, nothing will happen.
@@ -100,7 +99,7 @@ When everything's working, it's time to announce the release to the world!
 # Starting the next development version
 
 ```bash
-$ git checkout dev
+$ git checkout master
 $ vim constants.php
 # Update the FRESHRSS_VERSION
 $ vim CHANGELOG.md