fix feature-dependant argument options

src/arg.rs

@@ -1,6 +1,7 @@
 //! Argument parsing and handling
 use super::*;
 use std::num::NonZeroUsize;
+use std::fmt;
 
 use config::Config;
 
@@ -21,6 +22,40 @@ pub fn program_name() -> &'static str
     eprintln!("Made by {} with <3.\n Licensed with GPL v3.0 +", env!("CARGO_PKG_AUTHORS"));
 }
 
+const OPTIONS_NORMAL: &'static [&'static str] = &[
+    "--recursive <number>	Set max directory recursion depth limit (1 = No recursion (default), 0 = Unlimited recursion).",
+    "-r			Set unlimited directory recursion depth. (same as `--recursive 0`).",
+    "--threads <number>	Limit the maximum number of tasks allowed to process concurrently (Set to 0 for unlimited.)",
+    "-M			Set number of parallel running tasks to unlimited. (Same as `--threads 0`). (default).",
+    "-m			Limit number of parallel tasks to the number of active CPU processors.",
+    "-q			Quiet mode. Don't output info messages about successful `stat`ing.",
+    "-Q			Silent mode. Don't output any messages.",
+    "-v			Verbose mode. Output extra information.",
+    #[cfg(feature="inspect")] "--save <file>		Dump the collected data to this file for further inspection.",
+    #[cfg(feature="inspect")] "-D			Dump the collected data to `stdout` (see `--save`.)",
+    "-			Stop parsing arguments, treat all the rest as paths.",
+];
+
+fn get_opt_normal() -> impl fmt::Display
+{
+    #[derive(Debug)]
+    struct Opt;
+
+    impl fmt::Display for Opt
+    {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+	{
+	    for line in OPTIONS_NORMAL.iter()
+	    {
+		writeln!(f, " {}", line)?;
+	    }
+	    Ok(())
+	}
+    }
+
+    Opt
+}
+
 /// Print usage message
 pub fn usage()
 {
@@ -33,17 +68,7 @@ pub fn usage()
     println!("{} --help", program_name());
     println!(r#"
 OPTIONS:
- --recursive <number>	Set max directory recursion depth limit (1 = No recursion (default), 0 = Unlimited recursion).
- -r			Set unlimited directory recursion depth. (same as `--recursive 0`).
- --threads <number>	Limit the maximum number of tasks allowed to process concurrently (Set to 0 for unlimited.)
- -M			Set number of parallel running tasks to unlimited. (Same as `--threads 0`). (default).
- -m			Limit number of parallel tasks to the number of active CPU processors.
- -q			Quiet mode. Don't output info messages about successful `stat`ing.
- -Q			Silent mode. Don't output any messages.
- -v			Verbose mode. Output extra information.
- --save <file>		Dump the collected data to this file for further inspection (only available when compiled with feature `inspect`)
- -D			Dump the collected data to `stdout` (see `--save`) (only available when compiled with feature `inspect`)
- -			Stop parsing arguments, treat all the rest as paths. 
+{}
 
  --help			Print this message and exit.
 
@@ -52,7 +77,7 @@ NOTES:
  If parallelism is set to unlimited, there can be a huge syscall overhead. It is recommended to use `-m`.
 
  Symlinks are ignored while collection stat data. They will fail with message 'Unknown file type'. Symlinks are generally very small in the actual data they contain themselves, so this is *usually* unimportant.
-"#);
+"#, get_opt_normal());
 }
 
 /// Print usage message then exit with code 1.