dd: allow multiple occurences for iflag, oflag and conv

The iflag, oflag and conv cli arguments take a list of values
and the correct behavior is to collect all values from multiple
occurences of theme.

For example if we call `dd --iflag=directory --iflag=skip_bytes` this should
collect the two values, `directory` and `skip_bytes` for iflag.

The unittest was added for this case.

src/uu/dd/src/dd.rs

@@ -1060,8 +1060,11 @@ Printing performance stats is also triggered by the INFO signal (where supported
         .arg(
             Arg::new(options::CONV)
                 .long(options::CONV)
-                .overrides_with(options::CONV)
                 .takes_value(true)
+                .multiple_occurrences(true)
+                .use_delimiter(true)
+                .require_delimiter(true)
+                .multiple_values(true)
                 .require_equals(true)
                 .value_name("CONV")
                 .help("(alternatively conv=CONV[,CONV]) specifies a comma-separated list of conversion options or (for legacy reasons) file flags. Conversion options and file flags may be intermixed.
@@ -1098,8 +1101,11 @@ Conversion Flags:
         .arg(
             Arg::new(options::IFLAG)
                 .long(options::IFLAG)
-                .overrides_with(options::IFLAG)
                 .takes_value(true)
+                .multiple_occurrences(true)
+                .use_delimiter(true)
+                .require_delimiter(true)
+                .multiple_values(true)
                 .require_equals(true)
                 .value_name("FLAG")
                 .help("(alternatively iflag=FLAG[,FLAG]) a comma separated list of input flags which specify how the input source is treated. FLAG may be any of the input-flags or general-flags specified below.
@@ -1125,8 +1131,11 @@ General-Flags
         .arg(
             Arg::new(options::OFLAG)
                 .long(options::OFLAG)
-                .overrides_with(options::OFLAG)
                 .takes_value(true)
+                .multiple_occurrences(true)
+                .use_delimiter(true)
+                .require_delimiter(true)
+                .multiple_values(true)
                 .require_equals(true)
                 .value_name("FLAG")
                 .help("(alternatively oflag=FLAG[,FLAG]) a comma separated list of output flags which specify how the output source is treated. FLAG may be any of the output-flags or general-flags specified below.

src/uu/dd/src/parseargs.rs

@@ -414,16 +414,11 @@ fn parse_flag_list<T: std::str::FromStr<Err = ParseError>>(
     tag: &str,
     matches: &Matches,
 ) -> Result<Vec<T>, ParseError> {
-    let mut flags = Vec::new();
-
-    if let Some(comma_str) = matches.value_of(tag) {
-        for s in comma_str.split(',') {
-            let flag = s.parse()?;
-            flags.push(flag);
-        }
-    }
-
-    Ok(flags)
+    matches
+        .values_of(tag)
+        .unwrap_or_default()
+        .map(|f| f.parse())
+        .collect()
 }
 
 /// Parse Conversion Options (Input Variety)

src/uu/dd/src/parseargs/unit_tests.rs

@@ -300,7 +300,39 @@ fn test_status_level_noxfer() {
 }
 
 #[test]
-fn test_override_multiple_levels() {
+fn test_multiple_flags_options() {
+    let args = vec![
+        String::from("dd"),
+        String::from("--iflag=fullblock,directory"),
+        String::from("--iflag=skip_bytes"),
+        String::from("--oflag=direct"),
+        String::from("--oflag=dsync"),
+        String::from("--conv=ascii,ucase"),
+        String::from("--conv=unblock"),
+    ];
+    let matches = uu_app().try_get_matches_from(args).unwrap();
+
+    // iflag
+    let iflags = parse_flag_list::<Flag>(options::IFLAG, &matches).unwrap();
+    assert_eq!(
+        vec![Flag::FullBlock, Flag::Directory, Flag::SkipBytes],
+        iflags
+    );
+
+    // oflag
+    let oflags = parse_flag_list::<Flag>(options::OFLAG, &matches).unwrap();
+    assert_eq!(vec![Flag::Direct, Flag::Dsync], oflags);
+
+    // conv
+    let conv = parse_flag_list::<ConvFlag>(options::CONV, &matches).unwrap();
+    assert_eq!(
+        vec![ConvFlag::FmtEtoA, ConvFlag::UCase, ConvFlag::Unblock],
+        conv
+    );
+}
+
+#[test]
+fn test_override_multiple_options() {
     let args = vec![
         String::from("dd"),
         String::from("--if=foo.file"),
@@ -321,12 +353,6 @@ fn test_override_multiple_levels() {
         String::from("--status=noxfer"),
         String::from("--count=512"),
         String::from("--count=1024"),
-        String::from("--conv=ascii,ucase"),
-        String::from("--conv=ebcdic,lcase,unblock"),
-        String::from("--iflag=direct,nocache"),
-        String::from("--iflag=count_bytes,skip_bytes"),
-        String::from("--oflag=append,direct"),
-        String::from("--oflag=append,seek_bytes"),
     ];
 
     let matches = uu_app().try_get_matches_from(args).unwrap();
@@ -368,14 +394,6 @@ fn test_override_multiple_levels() {
             .unwrap()
     );
 
-    // conv
-    let exp = vec![ConvFlag::FmtEtoA, ConvFlag::LCase, ConvFlag::Unblock];
-    let act = parse_flag_list::<ConvFlag>("conv", &matches).unwrap();
-    assert_eq!(exp.len(), act.len());
-    for cf in &exp {
-        assert!(exp.contains(cf));
-    }
-
     // count
     assert_eq!(
         CountType::Bytes(1024),
@@ -389,26 +407,6 @@ fn test_override_multiple_levels() {
         .unwrap()
         .unwrap()
     );
-
-    // iflag
-    assert_eq!(
-        IFlags {
-            count_bytes: true,
-            skip_bytes: true,
-            ..IFlags::default()
-        },
-        parse_iflags(&matches).unwrap()
-    );
-
-    // oflag
-    assert_eq!(
-        OFlags {
-            seek_bytes: true,
-            append: true,
-            ..OFlags::default()
-        },
-        parse_oflags(&matches).unwrap()
-    );
 }
 
 // ----- IConvFlags/Output -----