Merge pull request #683 from cchantep/patch-2

Update run documentation

Author: fthomas

docs/running.md

@@ -15,7 +15,9 @@ sbt stage
   --env-var FOO=BAR
 ```
 
-Or,
+> If [Firejail](https://firejail.wordpress.com/) is not available locally, the option `--disable-sandbox` can be used (not recommanded for production environment).
+
+Or as a [Docker](https://www.docker.com/) container:
 
 ```bash
 sbt docker:publishLocal
@@ -32,7 +34,17 @@ docker run -v $STEWARD_DIR:/opt/scala-steward -it scala-steward:0.1.0-SNAPSHOT \
   --env-var FOO=BAR
 ```
 
-If you run Scala Steward for your own private projects, you can pass additional environment variables from the command line using the `--env-var` flag as shown in the examples above. You can use this to pass any credentials required by your projects to resolve any private dependencies, e.g.:
+The [`git-ask-pass` option](https://git-scm.com/docs/gitcredentials) must specify an executable file (script) that returns (on the stdout),
+
+- either the plain text password corresponding to the configured `${LOGIN}`,
+- or (recommanded) an authentication token corresponding to `${LOGIN}` (with appropriate permissions to watch the repositories; e.g. [Create a personal access token](https://help.github.com/en/articles/creating-a-personal-access-token-for-the-command-line) for GitHub).
+
+### Private repositories
+
+If you run Scala Steward for your own private projects, the option `--do-not-fork` can be required, not to fork.
+Instead it will create pull requests directly on the private repository (as soon as the `${LOGIN}` can).
+
+It can also be useful to pass additional environment variables from the command line using the `--env-var` flag as shown in the examples above. You can use this to pass any credentials required by your projects to resolve any private dependencies, e.g.:
 
 ```bash
 --env-var BINTRAY_USER=username \