no bug - doc: also promote git as a repo r=glob DONTBUILD

Differential Revision: https://phabricator.services.mozilla.com/D188393

docs/contributing/vcs/mercurial.rst

@@ -2,7 +2,7 @@ Mercurial Overview
 ==================
 
 Mercurial is a source-code management tool which allows users to keep track of changes to the source code locally and share their changes with others.
-We use it for the development of Firefox.
+We also support Git as VCS (see :ref:`Firefox Contributors' Quick Reference`).
 
 Installation
 ------------

docs/setup/linux_build.rst

@@ -98,9 +98,8 @@ the interactive setup process.
 
 .. note::
 
-    In general, the Firefox workflow works best with Mercurial. However,
-    if you'd prefer to use ``git``, you can grab the source code in
-    "git" form by running the bootstrap script with the ``vcs`` parameter:
+    To use ``git``, you can grab the source code in "git" form by running the
+    bootstrap script with the ``vcs`` parameter:
 
     .. code-block:: shell
 

docs/setup/macos_build.rst

@@ -80,9 +80,8 @@ the interactive setup process.
 
 .. note::
 
-    In general, the Firefox workflow works best with Mercurial. However,
-    if you'd prefer to use ``git``, you can grab the source code in
-    "git" form by running the bootstrap script with the ``vcs`` parameter:
+    To use ``git``, you can grab the source code in "git" form by running the
+    bootstrap script with the ``vcs`` parameter:
 
     .. code-block:: shell
 

docs/setup/windows_build.rst

@@ -63,9 +63,8 @@ the interactive setup process.
 
 .. note::
 
-    In general, the Firefox workflow works best with Mercurial. However,
-    if you'd prefer to use ``git``, you can grab the source code in
-    "git" form by running the bootstrap script with the ``vcs`` parameter:
+    To use ``git``, you can grab the source code in "git" form by running the
+    bootstrap script with the ``vcs`` parameter:
 
     .. code-block:: shell