build: rename debian/ as ubuntu-ppa/

This is to avoid a clash with downstream Debian which
also maintains a `debian/` directory.

debian/Dockerfile → ubuntu-ppa/Dockerfile

@@ -10,4 +10,4 @@ COPY release.sh release.sh
 
 WORKDIR /data
 
-CMD ["./debian/release.sh"]
+CMD ["./ubuntu-ppa/release.sh"]

debian/release.sh → ubuntu-ppa/release.sh

@@ -42,13 +42,13 @@ fi
 
 # Vendor the cargo dependencies
 cargo vendor
-tar cJf debian/vendor.tar.xz vendor
+tar cJf ubuntu-ppa/vendor.tar.xz vendor
 
 for series in "${SERIES[@]}"; do
     UBUNTU_VERSION=$(distro-info --series "${series}" -r | cut -d' ' -f1)
     BUILD_DIR="build-${series}"
     mkdir -p "${BUILD_DIR}"
-    cp -r debian "${BUILD_DIR}/debian"
+    cp -r ubuntu-ppa "${BUILD_DIR}/debian"
     cd "${BUILD_DIR}"
 
     # Update changelog for the specific series