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, 37 insertions, 0 deletions

diff --git a/clap/examples/15_custom_validator.rs b/clap/examples/15_custom_validator.rs
new file mode 100644
index 0000000..a5c0d42
--- /dev/null
+++ b/clap/examples/15_custom_validator.rs
@@ -0,0 +1,37 @@
+extern crate clap;
+
+use clap::{App, Arg};
+
+fn main() {
+    // You can define a function (or a closure) to use as a validator to argument values. The
+    // function must accept a String and return Result<(), String> where Err(String) is the message
+    // displayed to the user.
+
+    let matches = App::new("myapp")
+                        // Application logic goes here...
+                        .arg(Arg::with_name("input")
+                                     .help("the input file to use")
+                                     .index(1)
+                                     .required(true)
+                                     // You can pass in a closure, or a function
+                                     .validator(is_png))
+                        .get_matches();
+
+    // Here we can call .unwrap() because the argument is required.
+    println!("The .PNG file is: {}", matches.value_of("input").unwrap());
+}
+
+fn is_png(val: String) -> Result<(), String> {
+    // val is the argument value passed in by the user
+    // val has type of String.
+    if val.ends_with(".png") {
+        Ok(())
+    } else {
+        // clap automatically adds "error: " to the beginning
+        // of the message.
+        Err(String::from("the file format must be png."))
+    }
+    // Of course, you can do more complicated validation as
+    // well, but for the simplicity, this example only checks
+    // if the value passed in ends with ".png" or not.
+}