feat(xattr): attribute_display for linux compatibility

This will add custom formatting to "security.capability" attribute.
Adds capctl as a dependency only for linux.

Author: pineapplehunter

Cargo.lock

@@ -118,6 +118,7 @@ default-features = false
 
 [target.'cfg(target_os = "linux")'.dependencies]
 proc-mounts = "0.3"
+capctl = "0.2.4"
 
 [target.'cfg(unix)'.dependencies]
 uzers = "0.12.1"

Cargo.toml

@@ -588,7 +588,13 @@ const ATTRIBUTE_DISPLAYS: &[AttributeDisplay] = &[
     },
 ];
 
-#[cfg(not(target_os = "macos"))]
+#[cfg(target_os = "linux")]
+const ATTRIBUTE_DISPLAYS: &[AttributeDisplay] = &[AttributeDisplay {
+    attribute: "security.capability",
+    display: display_capability,
+}];
+
+#[cfg(not(any(target_os = "linux", target_os = "macos")))]
 const ATTRIBUTE_DISPLAYS: &[AttributeDisplay] = &[];
 
 // com.apple.lastuseddate is two 64-bit values representing the seconds and nano seconds
@@ -665,6 +671,17 @@ fn display_macl(attribute: &Attribute) -> Option<String> {
         })
 }
 
+// "security.capability" attribute represents capabilities in a binary format.
+// See "capabilities(7)"
+#[cfg(target_os = "linux")]
+fn display_capability(attribute: &Attribute) -> Option<String> {
+    attribute
+        .value
+        .as_ref()
+        .and_then(|v| capctl::FileCaps::unpack_attrs(v).ok())
+        .map(|caps| format!("{caps}"))
+}
+
 // plist::XmlWriter takes the writer instead of borrowing it.  This is a
 // wrapper around a borrowed vector that just forwards the Write trait
 // calls to the borrowed vector.