Add structopt dependency in version 0.3.7

This patch series replaces argparse with structopt in the argument
handling code. As a first step, we need structopt as a dependency.

Import subrepo structopt/:structopt at efbdda4753592e27bc430fb01f7b9650b2f3174d
Import subrepo bitflags/:bitflags at 30668016aca6bd3b02c766e8347e0b4080d4c296
Import subrepo clap/:clap at 784524f7eb193e35f81082cc69454c8c21b948f7
Import subrepo heck/:heck at 093d56fbf001e1506e56dbfa38631d99b1066df1
Import subrepo proc-macro-error/:proc-macro-error at 6c4cfe79a622c5de8ae68557993542be46eacae2
Import subrepo proc-macro2/:proc-macro2 at d5d48eddca4566e5438e8a2cbed4a74e049544de
Import subrepo quote/:quote at 727436c6c137b20f0f34dde5d8fda2679b9747ad
Import subrepo rustversion/:rustversion at 0c5663313516263059ce9059ef81fc7a1cf655ca
Import subrepo syn-mid/:syn-mid at 5d3d85414a9e6674e1857ec22a87b96e04a6851a
Import subrepo syn/:syn at e87c27e87f6f4ef8919d0372bdb056d53ef0d8f3
Import subrepo textwrap/:textwrap at abcd618beae3f74841032aa5b53c1086b0a57ca2
Import subrepo unicode-segmentation/:unicode-segmentation at 637c9874c4fe0c205ff27787faf150a40295c6c3
Import subrepo unicode-width/:unicode-width at 3033826f8bf05e82724140a981d5941e48fce393
Import subrepo unicode-xid/:unicode-xid at 4baae9fffb156ba229665b972a9cd5991787ceb7

1 files changed, 41 insertions, 0 deletions

diff --git a/clap/examples/16_app_settings.rs b/clap/examples/16_app_settings.rs
new file mode 100644
index 0000000..ab1d185
--- /dev/null
+++ b/clap/examples/16_app_settings.rs
@@ -0,0 +1,41 @@
+extern crate clap;
+
+use clap::{App, AppSettings, SubCommand};
+
+fn main() {
+    // You can use AppSettings to change the application level behavior of clap. .setting() function
+    // of App struct takes AppSettings enum as argument. There is also .settings() function which
+    // takes slice of AppSettings enum.  You can learn more about AppSettings in the documentation,
+    // which also has examples on each setting.
+    //
+    // This example will only show usage of one AppSettings setting. See documentation for more
+    // information.
+
+    let matches = App::new("myapp")
+                        .setting(AppSettings::SubcommandsNegateReqs)
+                                            // Negates requirement of parent command.
+
+                        .arg_from_usage("<input> 'input file to use'")
+                                            // Required positional argument called input.  This
+                                            // will be only required if subcommand is not present.
+
+                        .subcommand(SubCommand::with_name("test")
+                                                .about("does some testing"))
+                                            // if program is invoked with subcommand, you do not
+                                            // need to specify the <input> argument anymore due to
+                                            // the AppSettings::SubcommandsNegateReqs setting.
+
+                        .get_matches();
+
+    // Calling unwrap() on "input" would not be advised here, because although it's required,
+    // if the user uses a subcommand, those requirements are no longer required. Hence, we should
+    // use some sort of 'if let' construct
+    if let Some(inp) = matches.value_of("input") {
+        println!("The input file is: {}", inp);
+    }
+
+    match matches.subcommand() {
+        ("test", _) => println!("The 'test' subcommand was used"),
+        _           => unreachable!()
+    }
+}