Bug 1921556 - Add Git vcs args snippet to sections that use bootstrap.py r=sylvestre DONTBUILD

This will clarify when to use the `--vcs=git` argument during the setup
process to prevent people from accidentally setting up their repository
for Mercurial.

Differential Revision: https://phabricator.services.mozilla.com/D224259

docs/contributing/contribution_quickref.rst

@@ -55,6 +55,11 @@ To Setup Firefox On Windows
     $ mkdir mozilla-source
     $ cd mozilla-source
     $ wget https://hg.mozilla.org/mozilla-central/raw-file/default/python/mozboot/bin/bootstrap.py
+
+    # To use Git as your VCS
+    $ python3 bootstrap.py --vcs=git
+
+    # To use Mercurial as your VCS
     $ python3 bootstrap.py
 
 More information on :ref:`building Firefox for Windows <Building Firefox On Windows>`.
@@ -65,6 +70,11 @@ To Setup Firefox On macOS and Linux
 .. code-block:: shell
 
     $ curl https://hg.mozilla.org/mozilla-central/raw-file/default/python/mozboot/bin/bootstrap.py -O
+
+    # To use Git as your VCS
+    $ python3 bootstrap.py --vcs=git
+
+    # To use Mercurial as your VCS
     $ python3 bootstrap.py
 
 More information on :ref:`building Firefox for Linux <Building Firefox On Linux>` and :ref:`building Firefox for MacOS <Building Firefox On MacOS>`.
@@ -75,6 +85,11 @@ To Setup Firefox for Android
 .. code-block:: shell
 
     $ curl https://hg.mozilla.org/mozilla-central/raw-file/default/python/mozboot/bin/bootstrap.py -O
+
+    # To use Git as your VCS
+    $ python3 bootstrap.py --vcs=git
+
+    # To use Mercurial as your VCS
     $ python3 bootstrap.py
 
 More information on :ref:`building Firefox for Android <Firefox for Android>`

docs/setup/linux_build.rst

@@ -94,6 +94,11 @@ the interactive setup process.
 .. code-block:: shell
 
     curl https://hg.mozilla.org/mozilla-central/raw-file/default/python/mozboot/bin/bootstrap.py -O
+
+    # To use Git as your VCS
+    python3 bootstrap.py --vcs=git
+
+    # To use Mercurial as your VCS
     python3 bootstrap.py
 
 .. note::

docs/setup/macos_build.rst

@@ -74,6 +74,11 @@ the interactive setup process.
 .. code-block:: shell
 
     curl https://hg.mozilla.org/mozilla-central/raw-file/default/python/mozboot/bin/bootstrap.py -O
+
+    # To use Git as your VCS
+    python3 bootstrap.py --vcs=git
+
+    # To use Mercurial as your VCS
     python3 bootstrap.py
 
 .. note::

docs/setup/windows_build.rst

@@ -75,6 +75,11 @@ the interactive setup process.
     mkdir mozilla-source
     cd mozilla-source
     wget https://hg.mozilla.org/mozilla-central/raw-file/default/python/mozboot/bin/bootstrap.py
+
+    # To use Git as your VCS
+    python3 bootstrap.py --vcs=git
+
+    # To use Mercurial as your VCS
     python3 bootstrap.py
 .. note::