Restore use of 'help.format' configuration property in 'git help'

Commit 1cc8af0 "help: use HTML as the default help format on Windows"
lost the ability to make use of the help.format config value by forcing
the use of a compiled in default if no command-line argument was provided.
This commit restores the use of the help.format value if one is
available, overriding the compiled default.

Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/help.c

diff --git a/builtin/help.c b/builtin/help.c
index 536d4fd..8f9cd60 100644
--- a/builtin/help.c
+++ b/builtin/help.c
@@ -449,10 +449,10 @@
 	setup_git_directory_gently(&nongit);
 	git_config(git_help_config, NULL);
 
-	if (parsed_help_format == HELP_FORMAT_NONE)
-		help_format = parse_help_format(DEFAULT_HELP_FORMAT);
-	else
+	if (parsed_help_format != HELP_FORMAT_NONE)
 		help_format = parsed_help_format;
+	if (help_format == HELP_FORMAT_NONE)
+		help_format = parse_help_format(DEFAULT_HELP_FORMAT);
 
 	alias = alias_lookup(argv[0]);
 	if (alias && !is_git_command(argv[0])) {