feat: add File::section_ids() iterator and file::SectionMut::set_trust() #(1912)

That way it's easier to make changes to sections in a mutable instance of
Git configuration.

Author: Byron

gix-config/src/file/access/read_only.rs

@@ -410,6 +410,11 @@ impl<'event> File<'event> {
         self.section_order.iter().map(move |id| (&self.sections[id], *id))
     }
 
+    /// Return an iterator over all section ids, in order of occurrence in the file itself.
+    pub fn section_ids(&mut self) -> impl Iterator<Item = SectionId> + '_ {
+        self.section_order.iter().copied()
+    }
+
     /// Return an iterator over all sections along with non-section events that are placed right after them,
     /// in order of occurrence in the file itself.
     ///

gix-config/src/file/mutable/section.rs

@@ -3,9 +3,6 @@ use std::{
     ops::{Deref, Range},
 };
 
-use bstr::{BStr, BString, ByteSlice, ByteVec};
-use smallvec::SmallVec;
-
 use crate::{
     file::{
         self,
@@ -16,6 +13,9 @@ use crate::{
     parse::{section::ValueName, Event},
     value::{normalize, normalize_bstr, normalize_bstring},
 };
+use bstr::{BStr, BString, ByteSlice, ByteVec};
+use gix_sec::Trust;
+use smallvec::SmallVec;
 
 /// A opaque type that represents a mutable reference to a section.
 #[derive(PartialEq, Eq, Hash, PartialOrd, Ord, Debug)]
@@ -142,6 +142,14 @@ impl<'event> SectionMut<'_, 'event> {
         }
     }
 
+    /// Set the trust level in the meta-data of this section to `trust`.
+    pub fn set_trust(&mut self, trust: Trust) -> &mut Self {
+        let mut meta = (*self.section.meta).clone();
+        meta.trust = trust;
+        self.section.meta = meta.into();
+        self
+    }
+
     /// Removes the latest value by key and returns it, if it exists.
     pub fn remove(&mut self, value_name: &str) -> Option<Cow<'event, BStr>> {
         let key = ValueName::from_str_unchecked(value_name);