df: let the last of -B, -h, -H, -k and -m win, like GNU

src/uu/df/src/df.rs

@@ -48,6 +48,15 @@ static OPT_HUMAN_READABLE_DECIMAL: &str = "human-readable-decimal";
 static OPT_INODES: &str = "inodes";
 static OPT_KILO: &str = "kilo";
 static OPT_MEGA: &str = "mega";
+/// `-B`, `-h`, `-H`, `-k` and `-m` all pick how sizes are shown. Like GNU df,
+/// whichever comes last on the command line wins, so each overrides the others.
+static SIZE_OPTIONS: [&str; 5] = [
+    "blocksize",
+    "human-readable-binary",
+    "human-readable-decimal",
+    "kilo",
+    "mega",
+];
 static OPT_LOCAL: &str = "local";
 static OPT_NO_SYNC: &str = "no-sync";
 static OPT_OUTPUT: &str = "output";
@@ -564,7 +573,7 @@ pub fn uu_app() -> Command {
                 .short('B')
                 .long(OPT_BLOCKSIZE_LONG)
                 .value_name("SIZE")
-                .overrides_with_all([OPT_KILO, OPT_MEGA, OPT_BLOCKSIZE])
+                .overrides_with_all(SIZE_OPTIONS)
                 .help(translate!("df-help-block-size")),
         )
         .arg(
@@ -578,15 +587,15 @@ pub fn uu_app() -> Command {
             Arg::new(OPT_HUMAN_READABLE_BINARY)
                 .short('h')
                 .long("human-readable")
-                .overrides_with_all([OPT_HUMAN_READABLE_DECIMAL, OPT_HUMAN_READABLE_BINARY])
+                .overrides_with_all(SIZE_OPTIONS)
                 .help(translate!("df-help-human-readable"))
                 .action(ArgAction::SetTrue),
         )
         .arg(
             Arg::new(OPT_HUMAN_READABLE_DECIMAL)
                 .short('H')
                 .long("si")
-                .overrides_with_all([OPT_HUMAN_READABLE_BINARY, OPT_HUMAN_READABLE_DECIMAL])
+                .overrides_with_all(SIZE_OPTIONS)
                 .help(translate!("df-help-si"))
                 .action(ArgAction::SetTrue),
         )
@@ -602,14 +611,14 @@ pub fn uu_app() -> Command {
             Arg::new(OPT_KILO)
                 .short('k')
                 .help(translate!("df-help-kilo"))
-                .overrides_with_all([OPT_BLOCKSIZE, OPT_KILO, OPT_MEGA])
+                .overrides_with_all(SIZE_OPTIONS)
                 .action(ArgAction::SetTrue),
         )
         .arg(
             Arg::new(OPT_MEGA)
                 .short('m')
                 .help(translate!("df-help-mega"))
-                .overrides_with_all([OPT_BLOCKSIZE, OPT_KILO, OPT_MEGA])
+                .overrides_with_all(SIZE_OPTIONS)
                 .action(ArgAction::SetTrue),
         )
         .arg(

tests/by-util/test_df.rs

@@ -650,6 +650,43 @@ fn test_block_size_1m_option_with_output() {
     }
 }
 
+#[test]
+fn test_last_size_option_wins() {
+    // GNU df 9.11: -B, -h, -H, -k and -m override each other, the last one wins.
+    for (args, expected) in [
+        (&["-h", "-B", "1K"][..], "1K-blocks"),
+        (&["-B", "1K", "-h"][..], "Size"),
+        (&["-h", "-k"][..], "1K-blocks"),
+        (&["-k", "-h"][..], "Size"),
+        (&["-H", "-k"][..], "1K-blocks"),
+        (&["-k", "-H"][..], "Size"),
+        (&["-h", "-m"][..], "1M-blocks"),
+        (&["-m", "-h"][..], "Size"),
+    ] {
+        let output = new_ucmd!()
+            .args(args)
+            .arg("--output=size")
+            .succeeds()
+            .stdout_str_lossy();
+        let header = output.lines().next().unwrap().trim();
+
+        assert_eq!(header, expected, "df {}", args.join(" "));
+    }
+}
+
+#[test]
+fn test_block_size_after_human_readable_sets_the_values() {
+    // The header alone would pass if only the header code followed the order,
+    // so also check the value is a plain block count, not a human size like "461G".
+    let output = new_ucmd!()
+        .args(&["-h", "-B", "1", "--output=size", "."])
+        .succeeds()
+        .stdout_str_lossy();
+    let value = output.lines().nth(1).unwrap().trim();
+
+    assert!(value.chars().all(|c| c.is_ascii_digit()), "got {value}");
+}
+
 #[test]
 fn test_block_size_with_suffix() {
     fn get_header(block_size: &str) -> String {