Apply code review feedback: encapsulate optional field and move constant to module level

Co-authored-by: Byron <[email protected]>

Author: Copilot

gix-config-value/src/path.rs

@@ -4,6 +4,9 @@ use bstr::BStr;
 
 use crate::Path;
 
+/// The prefix used to mark a path as optional in Git configuration files.
+const OPTIONAL_PREFIX: &[u8] = b":(optional)";
+
 ///
 pub mod interpolate {
     use std::path::PathBuf;
@@ -108,8 +111,6 @@ impl AsRef<BStr> for Path<'_> {
 
 impl<'a> From<Cow<'a, BStr>> for Path<'a> {
     fn from(value: Cow<'a, BStr>) -> Self {
-        const OPTIONAL_PREFIX: &[u8] = b":(optional)";
-        
         // Check if the value starts with ":(optional)" prefix
         if value.starts_with(OPTIONAL_PREFIX) {
             // Strip the prefix while preserving the Cow variant to avoid unnecessary allocations
@@ -122,12 +123,12 @@ impl<'a> From<Cow<'a, BStr>> for Path<'a> {
             };
             Path {
                 value: stripped,
-                is_optional: true,
+                optional: true,
             }
         } else {
             Path {
                 value,
-                is_optional: false,
+                optional: false,
             }
         }
     }
@@ -140,7 +141,7 @@ impl<'a> Path<'a> {
     /// This is typically used for configuration like `blame.ignorerevsfile` where
     /// the file might not exist in all repositories.
     pub fn is_optional(&self) -> bool {
-        self.is_optional
+        self.optional
     }
 
     /// Interpolates this path into a path usable on the file system.

gix-config-value/src/types.rs

@@ -46,5 +46,6 @@ pub struct Path<'a> {
     /// The path string, un-interpolated
     pub value: std::borrow::Cow<'a, bstr::BStr>,
     /// Whether this path was prefixed with `:(optional)`, indicating it's acceptable if the file doesn't exist.
-    pub is_optional: bool,
+    /// Use `is_optional()` method to check this value.
+    pub(crate) optional: bool,
 }