docs: Fix stale examples

These were broken in #17 and #38 when renaming `hidden` to `hide`.  These
weren't caught because we test with `--all-targets` which is mutually
exclusive with `--doc`.

Makefile

@@ -26,3 +26,4 @@ build-%:
 
 test-%:
 	cargo test ${_FEATURES_${@:test-%=%}} --all-targets ${ARGS}
+	cargo test ${_FEATURES_${@:test-%=%}} --doc ${ARGS}

clap_generate/src/lib.rs

@@ -30,7 +30,7 @@
 //! fn build_cli() -> App<'static> {
 //!     App::new("example")
 //!          .arg(Arg::new("file")
-//!              .about("some input file")
+//!              .help("some input file")
 //!                 .value_hint(ValueHint::AnyPath),
 //!         )
 //!        .arg(
@@ -104,13 +104,13 @@ pub use shell::Shell;
 ///     App::new("compl")
 ///         .about("Tests completions")
 ///         .arg(Arg::new("file")
-///             .about("some input file"))
+///             .help("some input file"))
 ///         .subcommand(App::new("test")
 ///             .about("tests things")
 ///             .arg(Arg::new("case")
 ///                 .long("case")
 ///                 .takes_value(true)
-///                 .about("the case to test")))
+///                 .help("the case to test")))
 /// }
 /// ```
 ///

src/build/arg/mod.rs

@@ -2036,7 +2036,7 @@ impl<'help> Arg<'help> {
     /// // value with a help text
     ///     PossibleValue::new("slow").help("not that fast"),
     /// // value that is hidden from completion and help text
-    ///     PossibleValue::new("medium").hidden(true),
+    ///     PossibleValue::new("medium").hide(true),
     /// ])
     /// # ;
     /// ```
@@ -2113,7 +2113,7 @@ impl<'help> Arg<'help> {
     /// // value with a help text
     ///     .possible_value(PossibleValue::new("slow").help("not that fast"))
     /// // value that is hidden from completion and help text
-    ///     .possible_value(PossibleValue::new("medium").hidden(true))
+    ///     .possible_value(PossibleValue::new("medium").hide(true))
     /// # ;
     /// ```
     ///
@@ -3956,7 +3956,7 @@ impl<'help> Arg<'help> {
     /// let m = App::new("prog")
     ///     .arg(Arg::new("cfg")
     ///         .long("config")
-    ///         .hidden(true)
+    ///         .hide(true)
     ///         .help("Some help text describing the --config arg"))
     ///     .get_matches_from(vec![
     ///         "prog", "--help"