Update gitea

- rename the files
- fully qualify base
- add compose build

gitea.Dockerfile

@@ -0,0 +1,20 @@
+# syntax=docker/dockerfile:1
+# gentoo-gitea
+FROM registry.ceamac.ro/gentoo-base-busybox AS builder
+
+WORKDIR /workdir
+COPY --exclude=repos --exclude=bin . .
+RUN --mount=type=cache,target=/workdir/cache,sharing=locked <<-EOF
+	echo 'acct-user/git gitea -git' >> /etc/portage/package.use/gitea
+	emerge -1v --quiet-build=y acct-user/git
+	/bin/bash src/setup-gitea.sh /mnt/gentoo -j8
+EOF
+
+FROM scratch
+WORKDIR /
+EXPOSE 3000 32799
+VOLUME ["/etc/gitea", "/var/lib/gitea"]
+COPY --from=builder /mnt/gentoo /
+RUN tar c -j -f /var/db/pkg.tar.bz2 -C /var/db/pkg . && rm -fR /var/db/pkg
+USER git:git
+CMD ["/usr/bin/gitea", "web"]