feat(help): Explicit control over short/long help

Fixes #4687

clap_builder/src/builder/action.rs

@@ -257,6 +257,58 @@ pub enum ArgAction {
     /// # }
     /// ```
     Help,
+    /// When encountered, display [`Command::print_help`][super::Command::print_help]
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # #[cfg(feature = "help")] {
+    /// # use clap_builder as clap;
+    /// # use clap::Command;
+    /// # use clap::Arg;
+    /// let cmd = Command::new("mycmd")
+    ///     .arg(
+    ///         Arg::new("special-help")
+    ///             .short('?')
+    ///             .action(clap::ArgAction::HelpShort)
+    ///     );
+    ///
+    /// // Existing help still exists
+    /// let err = cmd.clone().try_get_matches_from(["mycmd", "-h"]).unwrap_err();
+    /// assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
+    ///
+    /// // New help available
+    /// let err = cmd.try_get_matches_from(["mycmd", "-?"]).unwrap_err();
+    /// assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
+    /// # }
+    /// ```
+    HelpShort,
+    /// When encountered, display [`Command::print_long_help`][super::Command::print_long_help]
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # #[cfg(feature = "help")] {
+    /// # use clap_builder as clap;
+    /// # use clap::Command;
+    /// # use clap::Arg;
+    /// let cmd = Command::new("mycmd")
+    ///     .arg(
+    ///         Arg::new("special-help")
+    ///             .short('?')
+    ///             .action(clap::ArgAction::HelpLong)
+    ///     );
+    ///
+    /// // Existing help still exists
+    /// let err = cmd.clone().try_get_matches_from(["mycmd", "-h"]).unwrap_err();
+    /// assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
+    ///
+    /// // New help available
+    /// let err = cmd.try_get_matches_from(["mycmd", "-?"]).unwrap_err();
+    /// assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
+    /// # }
+    /// ```
+    HelpLong,
     /// When encountered, display [`Command::version`][super::Command::version]
     ///
     /// Depending on the flag, [`Command::long_version`][super::Command::long_version] may be shown
@@ -299,6 +351,8 @@ impl ArgAction {
             Self::SetFalse => false,
             Self::Count => false,
             Self::Help => false,
+            Self::HelpShort => false,
+            Self::HelpLong => false,
             Self::Version => false,
         }
     }
@@ -311,6 +365,8 @@ impl ArgAction {
             Self::SetFalse => Some(std::ffi::OsStr::new("true")),
             Self::Count => Some(std::ffi::OsStr::new("0")),
             Self::Help => None,
+            Self::HelpShort => None,
+            Self::HelpLong => None,
             Self::Version => None,
         }
     }
@@ -323,6 +379,8 @@ impl ArgAction {
             Self::SetFalse => Some(std::ffi::OsStr::new("false")),
             Self::Count => None,
             Self::Help => None,
+            Self::HelpShort => None,
+            Self::HelpLong => None,
             Self::Version => None,
         }
     }
@@ -335,6 +393,8 @@ impl ArgAction {
             Self::SetFalse => Some(super::ValueParser::bool()),
             Self::Count => Some(crate::value_parser!(u8).into()),
             Self::Help => None,
+            Self::HelpShort => None,
+            Self::HelpLong => None,
             Self::Version => None,
         }
     }
@@ -348,6 +408,8 @@ impl ArgAction {
             Self::SetFalse => None,
             Self::Count => Some(AnyValueId::of::<CountType>()),
             Self::Help => None,
+            Self::HelpShort => None,
+            Self::HelpLong => None,
             Self::Version => None,
         }
     }

clap_builder/src/parser/parser.rs

@@ -1237,6 +1237,16 @@ impl<'cmd> Parser<'cmd> {
                 debug!("Help: use_long={use_long}");
                 Err(self.help_err(use_long))
             }
+            ArgAction::HelpShort => {
+                let use_long = false;
+                debug!("Help: use_long={use_long}");
+                Err(self.help_err(use_long))
+            }
+            ArgAction::HelpLong => {
+                let use_long = true;
+                debug!("Help: use_long={use_long}");
+                Err(self.help_err(use_long))
+            }
             ArgAction::Version => {
                 let use_long = match ident {
                     Some(Identifier::Long) => true,

tests/builder/help.rs

@@ -1063,6 +1063,65 @@ Options:
     utils::assert_output(cmd, "myapp --help", LONG_ABOUT, false);
 }
 
+#[test]
+fn explicit_short_long_help() {
+    static SHORT_ABOUT: &str = "\
+bar
+
+Usage: myapp [OPTIONS] [arg1]
+
+Arguments:
+  [arg1]  some option
+
+Options:
+  -?             
+  -h, --help     
+  -V, --version  Print version
+";
+
+    static LONG_ABOUT: &str = "\
+something really really long, with
+multiple lines of text
+that should be displayed
+
+Usage: myapp [OPTIONS] [arg1]
+
+Arguments:
+  [arg1]
+          some option
+
+Options:
+  -?
+          
+
+  -h, --help
+          
+
+  -V, --version
+          Print version
+";
+
+    let cmd = Command::new("myapp")
+        .disable_help_flag(true)
+        .version("1.0")
+        .author("foo")
+        .about("bar")
+        .long_about(
+            "something really really long, with\nmultiple lines of text\nthat should be displayed",
+        )
+        .arg(Arg::new("arg1").help("some option"))
+        .arg(Arg::new("short").short('?').action(ArgAction::HelpShort))
+        .arg(
+            Arg::new("long")
+                .short('h')
+                .long("help")
+                .action(ArgAction::HelpLong),
+        );
+    utils::assert_output(cmd.clone(), "myapp -?", SHORT_ABOUT, false);
+    utils::assert_output(cmd.clone(), "myapp -h", LONG_ABOUT, false);
+    utils::assert_output(cmd, "myapp --help", LONG_ABOUT, false);
+}
+
 #[test]
 fn ripgrep_usage() {
     static RIPGREP_USAGE: &str = "\