fix unread-fields warnings on latest nightly (#1330)

It's interesting to note that one of these warnings constitute
reading the fields, but these come about by displaying a
debug version of these fields, which now doesn't qualify anymore.

Author: Byron

gitoxide-core/src/repository/attributes/validate_baseline.rs

@@ -262,13 +262,18 @@ pub(crate) mod function {
     }
 
     #[derive(Debug)]
+    // See note on `Mismatch`
+    #[allow(dead_code)]
     pub struct ExcludeLocation {
         pub line: usize,
         pub rela_source_file: String,
         pub pattern: String,
     }
 
     #[derive(Debug)]
+    // We debug-print this structure, which makes all fields 'used', but it doesn't count.
+    // TODO: find a way to not have to do more work, but make the warning go away.
+    #[allow(dead_code)]
     pub enum Mismatch {
         Attributes {
             actual: Vec<gix::attrs::Assignment>,
@@ -281,6 +286,8 @@ pub(crate) mod function {
     }
 
     #[derive(Debug)]
+    // See note on `Mismatch`
+    #[allow(dead_code)]
     pub struct ExcludeMatch {
         pub pattern: gix::glob::Pattern,
         pub source: Option<PathBuf>,

gix-index/src/extension/fs_monitor.rs

@@ -6,6 +6,7 @@ use crate::{
 };
 
 #[derive(Clone)]
+#[allow(dead_code)]
 pub enum Token {
     V1 { nanos_since_1970: u64 },
     V2 { token: BString },