Add support for specifying alternative dockerfile names to the parser

Signed-off-by: Ethan Paul <ethan.paul@portalinstruments.com>

Author: enpaul

dockerfile_parse/parser.py

@@ -85,7 +85,8 @@ def __init__(self, path=None,
                  env_replace=True,
                  parent_env=None,
                  fileobj=None,
-                 build_args=None):
+                 build_args=None,
+                 dockerfile_filename=DOCKERFILE_FILENAME):
         """
         Initialize source of Dockerfile
         :param path: path to (directory with) Dockerfile; if not provided,
@@ -97,6 +98,8 @@ def __init__(self, path=None,
         :param fileobj: seekable file-like object containing Dockerfile content
                         as bytes (will be truncated on write)
         :param build_args: python dict of build args used when building image
+        :param dockerfile_filename: name of the dockerfile to discover or create
+                                    in the path (default: Dockerfile)
         """
 
         self.fileobj = fileobj
@@ -109,10 +112,10 @@ def __init__(self, path=None,
                 self.fileobj.seek(0)
         else:
             path = Path(path) or Path.cwd()
-            if path.name.endswith(DOCKERFILE_FILENAME):
+            if path.name.endswith(dockerfile_filename):
                 self.dockerfile = path
             else:
-                self.dockerfile = path / DOCKERFILE_FILENAME
+                self.dockerfile = path / dockerfile_filename
 
         self.cache_content = cache_content
         self.cached_content = ''  # unicode string