install: Clarify /boot (optional) and root mount spec

- /boot has been optional for a while
- Clarify the root uuid

Signed-off-by: Colin Walters <[email protected]>

Author: cgwalters

lib/src/install.rs

@@ -217,13 +217,15 @@ pub(crate) struct InstallTargetFilesystemOpts {
     pub(crate) root_path: Utf8PathBuf,
 
     /// Source device specification for the root filesystem.  For example, UUID=2e9f4241-229b-4202-8429-62d2302382e1
+    ///
+    /// If not provided, the UUID of the target filesystem will be used.
     #[clap(long)]
     pub(crate) root_mount_spec: Option<String>,
 
     /// Mount specification for the /boot filesystem.
     ///
-    /// At the current time, a separate /boot is required.  This restriction will be lifted in
-    /// future versions.  If not specified, the filesystem UUID will be used.
+    /// This is optional. If `/boot` is detected as a mounted partition, then
+    /// its UUID will be used.
     #[clap(long)]
     pub(crate) boot_mount_spec: Option<String>,