build: Work around OpenShift not including the .git directory

See e.g. openshift/source-to-image#457

Thankfully, OpenShift *will* do a recursive clone, so we don't
need to handle that.

Closes: #27

Dockerfile

@@ -1,4 +1,4 @@
 FROM registry.fedoraproject.org/fedora:28
 WORKDIR /root/src
 COPY . /root/src
-RUN ./build.sh
+RUN ./build.sh

build.sh

@@ -3,11 +3,17 @@ set -xeuo pipefail
 
 srcdir=$(pwd)
 
-# Init submodules
-ls -al .git mantle
-dnf -y install git
+# Work around https://github.com/coreos/coreos-assembler/issues/27
+if ! test -d .git; then
+    dnf -y install git
+    (git config --global user.email [email protected]
+     git init && git add . && git commit -a -m 'dummy commit'
+     git tag -m tag dummy-tag) >/dev/null
+fi
+
 if ! test -f mantle/README.md; then
-    git submodule update --init
+    echo "Run: git submodule update --init" 1>&2
+    exit 1
 fi
 
 # We want to run what builds we can as an unprivileged user;