[gimp] ci: Enable nightly flatpak builds

[Jehan <jehanp src gnome org>]

commit 83f5698fe248d6e279108c1e9f6780060dd1443c
Author: Ondřej Míchal <harrymichal seznam cz>
Date:   Mon Sep 7 15:49:37 2020 +0000

    ci: Enable nightly flatpak builds
    
    To get a nightly flatpak, GNOME project offers a CI template[0] that can
    be extended instead of having to define everything from scratch.
    
    At the core is the "flatpak" job that tries to build the flatpak. If the
    build finishes succesfully, the result should be available as a CI
    artifact as a flatpak bundle. The app id is the same as on Flathub.
    
    Another part is the "flatpak-nightly" job that publishes the flatpak if
    the build succeeded. Without this job, the bundle stays only temporarily.
    This job can and should only be run on the "master" branch. This jobs is
    started only when the "flatpak" job finishes successfully.
    
    Both jobs can be triggered only thorugh schedules[1]. To finish the
    flatpak nightlies setup, a schedule needs to be set.
    
    [0] https://gitlab.gnome.org/GNOME/Initiatives/-/wikis/DevOps-with-Flatpak
    [1] https://docs.gitlab.com/ee/ci/pipelines/schedules.html

 .gitlab-ci.yml | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 19397c7d55..54782478d0 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -6,6 +6,7 @@
 # - Win32 crossbuilds (rare usefulness)
 # - Linux CLang (rare usefulness)
 # - cppcheck (static code analysis)
+# - Flatpak build
 # Releases ($CI_COMMIT_TAG != null) should run only:
 # - Linux autotools (distcheck source tarball)
 # - Win 32/64 native builds (Windows installer creation)
@@ -23,6 +24,8 @@
 # - GIMP_CI_SOURCES: trigger the autotools/gcc build and the source tarball job.
 # - GIMP_CI_CPPCHECK: trigger cppcheck static analysis.
 
+include: 'https://gitlab.gnome.org/GNOME/citemplates/raw/master/flatpak/flatpak_ci_initiative.yml'
+
 image: debian:testing
 
 stages:
@@ -539,6 +542,30 @@ gimp-win32:
       - _build/
       - gimp-prefix/
 
+
+## Linux Flatpak nightly CI ##
+
+## To learn more about the CI, go to https://gitlab.gnome.org/GNOME/Initiatives/-/wikis/DevOps-with-Flatpak
+
+flatpak:
+  extends: .flatpak
+  stage: gimp
+  needs: []
+  when: always
+  only:
+    - schedules
+  variables:
+    GIT_SUBMODULE_STRATEGY: normal
+
+    # Replace with your manifest path
+    MANIFEST_PATH: "build/flatpak/org.gimp.GIMP-nightly.json"
+    RUNTIME_REPO: "https://nightly.gnome.org/gnome-nightly.flatpakrepo";
+    # Replace with your application name, as written in the manifest
+    FLATPAK_MODULE: "gimp"
+    APP_ID: "org.gimp.GIMP"
+    BUNDLE: "gimp-git.flatpak"
+
+
 cppcheck:
   rules:
     # Custom builds only (web GUI, API or schedules).
@@ -778,3 +805,12 @@ win32-nightly:
         python3 build/windows/gitlab-ci/dll_link.py $dll ${GIMP_PREFIX}/ ${GIMP_DISTRIB};
       done
   needs: ["gimp-win32", "deps-win64"]
+
+flatpak-nightly:
+  extends: '.publish_nightly'
+  stage: distribution
+  only:
+    - schedules
+  needs: ["flatpak"]
+  dependencies:
+    - 'flatpak'