Allow different filenames for Dockerfiles

In certain build projects, multiple Dockerfiles exist (for example,
one per distro) to simplify reading. However, this role is hardwired
to use dockerfiles only named "Dockerfile".

This is a problem, as you can't override the filename neither per
image, or globally.

This should fix the problem, allowing certain images to be build
by providing the dockerfile argument in docker_images, but also
have a globally overridable flag if you are using a different
convention (for example Dockerfile.distro_minordistroversion).

Change-Id: I075c365bc9f4f85f9ada832d22d1f1e213e68e21

roles/build-docker-image/common.rst

@@ -42,6 +42,15 @@ using this role.
    The project directory.  Serves as the base for
    :zuul:rolevar:`build-docker-image.docker_images.context`.
 
+.. zuul:rolevar:: docker_dockerfile
+   :default: Dockerfile
+
+   The default Dockerfile name to use. Serves as the base for
+   :zuul:rolevar:`build-docker-image.docker_images.dockerfile`.
+   This allows a global overriding of Dockerfile name, for example
+   when building all images from different folders with similarily
+   named dockerfiles.
+
 .. zuul:rolevar:: docker_credentials
    :type: dict
 
@@ -75,6 +84,12 @@ using this role.
       The docker build context; this should be a directory underneath
       :zuul:rolevar:`build-docker-image.zuul_work_dir`.
 
+   .. zuul:rolevar:: dockerfile
+
+      The filename of the dockerfile, present in the context folder,
+      used for building the image. Provide this if you are using
+      a non-standard filename for a specific image.
+
    .. zuul:rolevar:: repository
 
       The name of the target repository in dockerhub for the

roles/build-docker-image/defaults/main.yaml

@@ -1 +1,2 @@
 zuul_work_dir: "{{ zuul.project.src_dir }}"
+docker_dockerfile: "Dockerfile"

roles/build-docker-image/tasks/main.yaml

@@ -1,6 +1,6 @@
 - name: Build a docker image
   command: >-
-    docker build {{ item.path | default('.') }} -f Dockerfile
+    docker build {{ item.path | default('.') }} -f {{ item.dockerfile | default(docker_dockerfile) }}
     {% if item.target | default(false) -%}
       --target {{ item.target }}
     {% endif -%}