ci/install-dependencies: handle "sparse" job package installs

This just matches the style/location of the package installation for
other jobs. There should be no functional change.

I did flip the order of the options and command-name ("-y update"
instead of "update -y") for consistency with other lines in the same
file.

Note also that we have to reorder the dependency install with the
"checkout" action, so that we actually have the "ci" scripts available.

Signed-off-by: Jeff King <peff@peff.net>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 0187888..224c46b 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -366,11 +366,9 @@
         artifact: sparse-20.04
     - name: Install the current `sparse` package
       run: sudo dpkg -i sparse-20.04/sparse_*.deb
-    - name: Install other dependencies
-      run: |
-        sudo apt-get update -q &&
-        sudo apt-get install -q -y libssl-dev libcurl4-openssl-dev libexpat-dev gettext zlib1g-dev
     - uses: actions/checkout@v2
+    - name: Install other dependencies
+      run: ci/install-dependencies.sh
     - run: make sparse
   documentation:
     needs: ci-config
diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 67852d0..5772081 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -65,6 +65,11 @@
 	sudo apt-get -q -y install coccinelle libcurl4-openssl-dev libssl-dev \
 		libexpat-dev gettext make
 	;;
+sparse)
+	sudo apt-get -q update -q
+	sudo apt-get -q -y install libssl-dev libcurl4-openssl-dev \
+		libexpat-dev gettext zlib1g-dev
+	;;
 Documentation)
 	sudo apt-get -q update
 	sudo apt-get -q -y install asciidoc xmlto docbook-xsl-ns make