umoci config: disable flag argument re-ordering

It turns out that urfave/cli hasn't been happy with parsing
command-lines like [--config.cmd -c] for quite some time, and only just
exposed the issue in a test-case[1]. There are loads of more subtle
cases where you could see this happened even in the version of
urfave/cli we have vendored.

Until it's fixed upstream (which might not happen), we have to work
around this by disabling argument reordering for 'umoci config' (which
is the only command that usually has to deal with such flag arguments,
and luckily doesn't take any positional arguments).

[1]: urfave/cli#1152

Signed-off-by: Aleksa Sarai <asarai@suse.de>

CHANGELOG.md

@@ -13,8 +13,12 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased] ##
+### Fixed ###
 - Suppress repeated xattr warnings on destination filesystems that do not
-  support xattrs.
+  support xattrs. opencontainers/umoci#311
+- Work around a long-standing issue in our command-line parsing library (see
+  urfave/cli#1152) by disabling argument re-ordering for `umoci config`, which
+  often takes `-`-prefixed flag arguments. opencontainers/umoci#328
 
 ## [0.4.5] - 2019-12-04 ##
 ### Added ###

cmd/umoci/config.go

@@ -59,6 +59,18 @@ image.`,
 		return nil
 	},
 
+	// Do not re-order arguments.
+	//
+	// It turns out that urfave/cli incorrectly handles cases like
+	// [--config.cmd -c] during argument re-ordering for subcommands, causing
+	// us a fair number of issues when users are trying to pass a flag an
+	// argument that starts with a dash. Luckily 'umoci config' doesn't take
+	// positional arguments, so disabling argument re-ordering has no other
+	// real effect.
+	//
+	// See <https://github.com/urfave/cli/issues/1152> for more details.
+	SkipArgReorder: true,
+
 	Flags: []cli.Flag{
 		cli.StringFlag{Name: "config.user"},
 		cli.StringSliceFlag{Name: "config.exposedports"},