[gtk/commit-docs] docs: Clarify the section on commit access

[Emmanuele Bassi <ebassi src gnome org>]

commit 8629559ca29dc15a93e86d98001cd08713d9e535
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Mon Oct 15 10:48:05 2018 +0100

    docs: Clarify the section on commit access
    
    The section is about rules for direct commit access to the upstream
    repository, so let's be more clear about it.

 CONTRIBUTING.md | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)
---
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 301782e39f..70b7885e48 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -207,7 +207,7 @@ Closes: https://gitlab.gnome.org/GNOME/gtk/issues/1234
  the commit message, e.g. `Bug: #1234`, and use the automatic issue
  closing syntax in the description of the merge request.
 
-### Access to the GTK repository
+### Commit access to the GTK repository
 
 GTK is part of the GNOME infrastructure. At the current time, any
 person with write access to the GNOME repository can make changes to
@@ -235,10 +235,11 @@ people committing to GTK+ to follow a few rules:
 0. Always write a meaningful commit message. Changes without a sufficient
    commit message will be reverted.
 
-0. Never push to a public branch directly; you should always go through
-   a merge request, to ensure that the code is tested on the CI infrastructure
-   at the very least. A merge request is also the proper place to get a
-   comprehensive code review from the core developers of GTK.
+0. Never push to the `master` branch, or any stable branches, directly; you
+   should always go through a merge request, to ensure that the code is
+   tested on the CI infrastructure at the very least. A merge request is
+   also the proper place to get a comprehensive code review from the core
+   developers of GTK.
 
 If you have been contributing to GTK for a while and you don't have commit
 access to the repository, you may ask to obtain it following the [GNOME account