merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/ci/run-linux32-docker.sh

@@ -0,0 +1,31 @@
+#!/bin/sh
+#
+# Download and run Docker image to build and test 32-bit Git
+#
+
+. ${0%/*}/lib.sh
+
+docker pull daald/ubuntu32:xenial
+
+# Use the following command to debug the docker build locally:
+# $ docker run -itv "${PWD}:/usr/src/git" --entrypoint /bin/bash daald/ubuntu32:xenial
+# root@container:/# /usr/src/git/ci/run-linux32-build.sh <host-user-id>
+
+container_cache_dir=/tmp/travis-cache
+
+docker run \
+	--interactive \
+	--env DEVELOPER \
+	--env DEFAULT_TEST_TARGET \
+	--env GIT_PROVE_OPTS \
+	--env GIT_TEST_OPTS \
+	--env GIT_TEST_CLONE_2GB \
+	--env cache_dir="$container_cache_dir" \
+	--volume "${PWD}:/usr/src/git" \
+	--volume "$cache_dir:$container_cache_dir" \
+	daald/ubuntu32:xenial \
+	/usr/src/git/ci/run-linux32-build.sh $(id -u $USER)
+
+check_unignored_build_artifacts
+
+save_good_tree