docker: docker.py don't conflate checksums for extra_files

This just gets confusing especially as the helper function doesn't
even take into account any extra files (or the executable). Currently
the actual check just ignores them and also passes the result through
_dockerfile_preprocess so we fix that too.
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>

tests/docker/docker.py

@@ -206,8 +206,10 @@ class Docker(object):
 
         tmp_df.write("\n")
         tmp_df.write("LABEL com.qemu.dockerfile-checksum=%s" %
-                     _text_checksum("\n".join([dockerfile] +
-                                    extra_files_cksum)))
+                     _text_checksum(_dockerfile_preprocess(dockerfile)))
+        for f, c in extra_files_cksum:
+            tmp_df.write("LABEL com.qemu.%s-checksum=%s" % (f, c))
+
         tmp_df.flush()
 
         self._do_check(["build", "-t", tag, "-f", tmp_df.name] + argv + \
@@ -322,7 +324,7 @@ class BuildCommand(SubCommand):
                 _copy_binary_with_libs(args.include_executable, docker_dir)
             for filename in args.extra_files or []:
                 _copy_with_mkdir(filename, docker_dir)
-                cksum += [_file_checksum(filename)]
+                cksum += [(filename, _file_checksum(filename))]
 
             argv += ["--build-arg=" + k.lower() + "=" + v
                         for k, v in os.environ.iteritems()