Add repoman.

repoman.Dockerfile

@@ -0,0 +1,35 @@
+# Portage tree.
+FROM gentoo/portage:latest as portage
+
+# Build packages in /workdir.
+FROM gentoo/stage3-amd64:latest as build
+COPY --from=portage /var/db/repos/gentoo /var/db/repos/gentoo
+ENV MAKEOPTS "-j1"
+ENV USE "minimal -cracklib -curl -gpg -idn -ncurses -net -nls"
+ENV USE "${USE} -pam -pcre -perl -readline -rsync-verify -ssl -webdav"
+ENV FEATURES "-ipc-sandbox -network-sandbox -pid-sandbox -sandbox -usersandbox"
+RUN eselect profile set default/linux/amd64/17.1/no-multilib
+RUN emerge --root=/workdir --quiet app-portage/repoman dev-vcs/git
+RUN emerge --root=/workdir --rage-clean --quiet \
+    app-arch/tar \
+    app-arch/xz-utils \
+    dev-libs/openssl \
+    net-dns/libidn2 \
+    net-misc/rsync \
+    sys-apps/file \
+    sys-apps/sed
+
+# Final image.
+FROM gentoo/portage:latest
+LABEL maintainer="tastytea+docker@tastytea.de"
+LABEL description="Latest stable app-portage/repoman."
+COPY --from=build /workdir /
+RUN eselect profile set default/linux/amd64/17.1/no-multilib
+# Bug 680456.
+RUN echo 'FEATURES="-ipc-sandbox -network-sandbox"' >> /etc/portage/make.conf
+# repoman needs portage user and group.
+RUN echo 'portage:x:250:250:portage:/var/tmp/portage:/bin/false' >> /etc/passwd
+RUN echo 'portage::250:portage' >> /etc/group
+
+# TODO: Mount distfiles.
+# TODO: Use ccache with data on external volume.