podman_image: add file parameter for Containerfile location (#492)

* `podman_image`: correct `path` parameter description

The `path` parameter is the last parameter when running `podman build
...`. As specified in the manpage, it is defined as the build context,
and not necessarily should it contain the Containerfile.

Signed-off-by: Yuriy Gabuev <yuriy.gabuev@holoplot.com>

* `podman_image`: add `file` parameter for Containerfile location

Add the `file` parameter to `podman_image` module which mirrors the
`--file` command line argument for `podman build ...`. This parameter
specifies the location of the Containerfile to use in case it should be
different from the one contained in the build context directory.

Signed-off-by: Yuriy Gabuev <yuriy.gabuev@holoplot.com>

* `podman_image`: add integration tests for `file` parameter

Add tests to ensure that:
- building from a directory without a Containerfile (or Dockerfile)
  fails
- specifying the location of Containerfile with `file` parameter works

Signed-off-by: Yuriy Gabuev <yuriy.gabuev@holoplot.com>

Signed-off-by: Yuriy Gabuev <yuriy.gabuev@holoplot.com>

plugins/modules/podman_image.py

@@ -43,7 +43,7 @@ DOCUMENTATION = r'''
       default: False
       type: bool
     path:
-      description: Path to directory containing the build file.
+      description: Path to the build context directory.
       type: str
     force:
       description:
@@ -88,6 +88,10 @@ DOCUMENTATION = r'''
         - build_args
         - buildargs
       suboptions:
+        file:
+          description:
+            - Path to the Containerfile if it is not in the build context directory.
+          type: path
         volume:
           description:
             - Specify multiple volume / mount options to mount one or more mounts to a container.
@@ -606,6 +610,10 @@ class PodmanImageManager(object):
         if self.build.get('rm'):
             args.append('--rm')
 
+        containerfile = self.build.get('file')
+        if containerfile:
+            args.extend(['--file', containerfile])
+
         volume = self.build.get('volume')
         if volume:
             for v in volume:
@@ -767,6 +775,7 @@ def main():
                 options=dict(
                     annotation=dict(type='dict'),
                     force_rm=dict(type='bool', default=False),
+                    file=dict(type='path'),
                     format=dict(
                         type='str',
                         choices=['oci', 'docker'],