import-spec: script for importing upstream spec

The canonical spec file is now upstream since:
https://github.com/projectatomic/rpm-ostree/pull/1900

Add a script to make it trivial to import the spec file here and merge
the changelog. There's a `--keep-v-r` flag one can use to keep the
Version and Release tags of the existing spec file to deal with e.g. git
snapshots (though ideally continuous builds will eventually be handled
automatically).

import-spec

@@ -0,0 +1,54 @@
+#!/bin/bash
+set -euo pipefail
+
+KEEP_V_R=
+while [ $# -gt 0 ]; do
+    case "$1" in
+        -h | --help)
+            echo "Usage: $0 [--keep-v-r]" >&2
+            exit 0
+            ;;
+        --keep-v-r)
+            KEEP_V_R=1
+            ;;
+        *)
+            echo "$0: unrecognized option: $1" >&2
+            exit 1
+            ;;
+    esac
+    shift
+done
+
+main() {
+    local upstream
+    upstream=$(get_parsed_spec_field URL)
+    curl -Lo rpm-ostree.spec.new "$upstream/raw/master/packaging/rpm-ostree.spec.in"
+    sed -ne '/%changelog/,$ p' rpm-ostree.spec >> rpm-ostree.spec.new
+
+    if [ -n "${KEEP_V_R}" ]; then
+        local version release
+        version=$(get_raw_spec_field Version)
+        release=$(get_raw_spec_field Release)
+
+        sed -ie "s/^Version:.*/Version: $version/" rpm-ostree.spec.new
+        sed -ie "s/^Release:.*/Release: $release/" rpm-ostree.spec.new
+    fi
+
+    if git diff --quiet --exit-code rpm-ostree.spec; then
+        mv rpm-ostree.spec.new rpm-ostree.spec
+        echo "Updated rpm-ostree.spec" >&2
+    else
+        echo "Refusing to overwrite dirty rpm-ostree.spec" >&2
+        echo "Updated rpm-ostree.spec.new" >&2
+    fi
+}
+
+get_parsed_spec_field() {
+    rpmspec -P rpm-ostree.spec | grep "^${1}: " | head -n1 | cut -d ' ' -f 2
+}
+
+get_raw_spec_field() {
+    grep "^${1}: " rpm-ostree.spec | head -n1 | cut -d ' ' -f 2
+}
+
+main "$@"