ci: introduce Packit

Build (and test) dbus-broker on Fedora Rawhide using Packit. This uses
Fedora's spec file to build an SRPM, which is then submitted to Copr &
built.

Replaces: #279

.packit.yml

@@ -0,0 +1,40 @@
+---
+# vi:ts=2 sw=2 et:
+#
+# Docs: https://packit.dev/docs/
+
+specfile_path: .packit_rpm/dbus-broker.spec
+files_to_sync:
+  - .packit.yml
+  - src: .packit_rpm/dbus-broker.spec
+    dest: dbus-broker.spec
+upstream_package_name: dbus-broker
+downstream_package_name: dbus-broker
+upstream_tag_template: "v{version}"
+
+actions:
+  post-upstream-clone:
+    # Download all subprojects in advance, as we won't have networking during RPM build
+    - "meson subprojects download"
+    # Use the Fedora Rawhide specfile
+    - "git clone https://src.fedoraproject.org/rpms/dbus-broker .packit_rpm --depth=1"
+    # Drop the "sources" file so rebase-helper doesn't think we're a dist-git
+    - "rm -fv .packit_rpm/sources"
+    # Drop backported patches from the specfile
+    - "sed -ri '/^Patch.*\\:.+\\.patch/d' .packit_rpm/dbus-broker.spec"
+
+  create-archive:
+    # We have to override the default archive command (which is 'git archive'), since that ignores
+    # files in subprojects
+    - 'bash -c "tar -pczf .packit_rpm/$PACKIT_PROJECT_NAME_VERSION.tar.gz --exclude=.packit_rpm --transform \"s/^\./$PACKIT_PROJECT_NAME_VERSION/\" ."'
+    - 'bash -c "echo .packit_rpm/$PACKIT_PROJECT_NAME_VERSION.tar.gz"'
+
+jobs:
+- job: copr_build
+  trigger: pull_request
+  targets:
+  - fedora-rawhide-aarch64
+  - fedora-rawhide-i386
+  - fedora-rawhide-ppc64le
+  - fedora-rawhide-s390x
+  - fedora-rawhide-x86_64