Use `--depth` flag to `git clone` in Dockerfiles, to save space

optimize the git clone using --depth flag in term of size of clone
and also in term's of time taken to fetch the files and commit history
of whole repository .

More detail can be found at blog
https://www.atlassian.com/git/tutorials/big-repositories

Signed-off-by: Pratik Raj <rajpratik71@gmail.com>
Change-Id: Ia25d420b2835f8decdcd69490afb259f464295e0
diff --git a/trellis/docker/Dockerfile b/trellis/docker/Dockerfile
index b799dbc..e6146a4 100644
--- a/trellis/docker/Dockerfile
+++ b/trellis/docker/Dockerfile
@@ -12,7 +12,7 @@
     rm -rf /var/lib/apt/lists/*
 
 # Install Quagga
-RUN git clone -b onos-1.11 https://gerrit.opencord.org/quagga
+RUN git clone --depth 1 -b onos-1.11 https://gerrit.opencord.org/quagga
 WORKDIR $HOME/quagga
 RUN ./bootstrap.sh
 RUN ./configure --enable-fpm --sbindir=/usr/lib/quagga enable_user=root enable_group=root
@@ -21,7 +21,7 @@
 
 # Clone Trellis simulation repo
 WORKDIR $HOME
-RUN git clone https://gerrit.onosproject.org/routing
+RUN git clone --depth 1 https://gerrit.onosproject.org/routing
 
 # Update dynamic linker
 RUN ldconfig