feat: show Btrfs subvolumes

src/fs/file.rs

@@ -400,6 +400,46 @@ impl<'dir> File<'dir> {
                 .is_some_and(|p| all_mounts().contains_key(p))
     }
 
+    /// Whether the directory represents a Btrfs subvolume
+    #[cfg(target_os = "linux")]
+    pub fn is_btrfs_subvolume(&self) -> bool {
+        // Listing all subvolumes with ioctl(BTRFS_IOC_TREE_SEARCH) requires CAP_SYS_ADMIN, normal users can't do that.
+        // So we test the inode number, directory representing a subvolume has always inode number 256
+        const BTRFS_FIRST_FREE_OBJECTID: u64 = 256;
+
+        self.is_directory()
+            && self.inode().0 == BTRFS_FIRST_FREE_OBJECTID
+            && self.is_btrfs().unwrap_or(false)
+    }
+
+    #[cfg(not(target_os = "linux"))]
+    pub fn is_btrfs_subvolume(&self) -> bool {
+        false
+    }
+
+    #[cfg(target_os = "linux")]
+    fn is_btrfs(&self) -> io::Result<bool> {
+        use std::os::unix::ffi::OsStrExt;
+
+        const BTRFS_FSTYPE_NAME: &str = "btrfs";
+
+        for part in self.absolute_path().unwrap_or(&self.path).ancestors() {
+            if let Some(mount) = all_mounts().get(part) {
+                return Ok(mount.fstype == BTRFS_FSTYPE_NAME);
+            }
+        }
+
+        // /proc/mounts not working? fallback to statfs
+        let file_path = &self.path;
+        let mut out = std::mem::MaybeUninit::<libc::statfs>::uninit();
+        let path = std::ffi::CString::new(file_path.as_os_str().as_bytes()).unwrap();
+        match unsafe { libc::statfs(path.as_ptr(), out.as_mut_ptr()) } {
+            0 => Ok(unsafe { out.assume_init() }.f_type == libc::BTRFS_SUPER_MAGIC),
+            _ => Err(io::Error::last_os_error()),
+            // eprintln!("eza: statfs {:?}: {}", self.path, os_err);
+        }
+    }
+
     /// The filesystem device and type for a mount point
     pub fn mount_point_info(&self) -> Option<&MountedFs> {
         if cfg!(any(target_os = "linux", target_os = "macos")) {

src/options/config.rs

@@ -266,6 +266,7 @@ pub struct FileKindsOverride {
     pub special: Option<StyleOverride>,       // sp
     pub executable: Option<StyleOverride>,    // ex
     pub mount_point: Option<StyleOverride>,   // mp
+    pub btrfs_subvol: Option<StyleOverride>,  // sv
 }
 
 impl FromOverride<FileKindsOverride> for FileKinds {
@@ -281,6 +282,7 @@ impl FromOverride<FileKindsOverride> for FileKinds {
             special: FromOverride::from(value.special, default.special),
             executable: FromOverride::from(value.executable, default.executable),
             mount_point: FromOverride::from(value.mount_point, default.mount_point),
+            btrfs_subvol: FromOverride::from(value.btrfs_subvol, default.btrfs_subvol),
         }
     }
 }

src/output/file_name.rs

@@ -488,6 +488,7 @@ impl<'a, 'dir, C: Colours> FileName<'a, 'dir, C> {
         #[rustfmt::skip]
         return match self.file {
             f if f.is_mount_point()      => self.colours.mount_point(),
+            f if f.is_btrfs_subvolume()  => self.colours.btrfs_subvol(),
             f if f.is_directory()        => self.colours.directory(),
             #[cfg(unix)]
             f if f.is_executable_file()  => self.colours.executable_file(),
@@ -541,6 +542,9 @@ pub trait Colours: FiletypeColours {
     /// The style to paint a directory that has a filesystem mounted on it.
     fn mount_point(&self) -> Style;
 
+    /// The style to paint a directory representing a Btrfs subvolume.
+    fn btrfs_subvol(&self) -> Style;
+
     fn colour_file(&self, file: &File<'_>) -> Style;
 
     fn style_override(&self, file: &File<'_>) -> Option<FileNameStyle>;

src/theme/default_theme.rs

@@ -36,6 +36,7 @@ impl Default for UiStyles {
             special: Some(Yellow.normal()),
             executable: Some(Green.bold()),
             mount_point: Some(Blue.bold().underline()),
+            btrfs_subvol: Some(Blue.underline()),
             }),
 
             #[rustfmt::skip]

src/theme/mod.rs

@@ -412,6 +412,9 @@ impl FileNameColours for Theme {
     fn broken_control_char(&self) -> Style { apply_overlay(self.ui.control_char(),   self.ui.broken_path_overlay()) }
     fn executable_file(&self)     -> Style { self.ui.filekinds.unwrap_or_default().executable() }
     fn mount_point(&self)         -> Style { self.ui.filekinds.unwrap_or_default().mount_point() }
+    fn btrfs_subvol(&self) -> Style {
+        self.ui.filekinds.unwrap_or_default().btrfs_subvol()
+    }
 
     fn colour_file(&self, file: &File<'_>) -> Style {
         self.exts
@@ -643,6 +646,7 @@ mod customs_test {
     test!(exa_bo:  ls "", exa "bO=4"         =>  colours c -> { c.broken_path_overlay                   = Some(Style::default().underline()); });
 
     test!(exa_mp:  ls "", exa "mp=1;34;4"    =>  colours c -> { c.filekinds().mount_point                 = Some(Blue.bold().underline()); });
+    test!(exa_sv:  ls "", exa "sv=0;34;4"    =>  colours c -> { c.filekinds().btrfs_subvol                = Some(Blue.underline()); });
     test!(exa_sp:  ls "", exa "sp=1;35;4"    =>  colours c -> { c.filekinds().special                     = Some(Purple.bold().underline()); });
 
     test!(exa_im:  ls "", exa "im=38;5;128"  =>  colours c -> { c.file_type().image                       = Some(Fixed(128).normal()); });

src/theme/ui_styles.rs

@@ -125,6 +125,7 @@ pub struct FileKinds {
     pub special: Option<Style>,       // sp
     pub executable: Option<Style>,    // ex
     pub mount_point: Option<Style>,   // mp
+    pub btrfs_subvol: Option<Style>,  // sv
 }
 
 impl Default for FileKinds {
@@ -140,6 +141,7 @@ impl Default for FileKinds {
             special: Some(Yellow.normal()),
             executable: Some(Green.bold()),
             mount_point: Some(Blue.bold().underline()),
+            btrfs_subvol: Some(Blue.underline()),
         }
     }
 }
@@ -154,7 +156,8 @@ field_accessors!(
     socket: Option<Style>,
     special: Option<Style>,
     executable: Option<Style>,
-    mount_point: Option<Style>
+    mount_point: Option<Style>,
+    btrfs_subvol: Option<Style>
 );
 
 #[rustfmt::skip]
@@ -397,6 +400,7 @@ impl UiStyles {
             special: Some(Style::default()),
             executable: Some(Style::default()),
             mount_point: Some(Style::default()),
+            btrfs_subvol: Some(Style::default()),
             }),
 
             #[rustfmt::skip]
@@ -596,6 +600,7 @@ impl UiStyles {
             "bO" => self.broken_path_overlay             = Some(pair.to_style()),
 
             "mp" => self.filekinds().mount_point          = Some(pair.to_style()),
+            "sv" => self.filekinds().btrfs_subvol         = Some(pair.to_style()),
             "sp" => self.filekinds().special              = Some(pair.to_style()),  // Catch-all for unrecognized file kind
 
             "im" => self.file_type().image                = Some(pair.to_style()),