fix: Assure gix-submodule works with Rust 1.65.

The previous version of this loop, possibly preferable, ran into
a borrow-check issue that was no more from Rust 1.70 onwards.

.github/workflows/msrv.yml

@@ -20,6 +20,6 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3
-      - uses: dtolnay/[email protected] # dictated by `windows` crates effectively, IMPORTANT: adjust etc/msrv-badge.svg as well
+      - uses: dtolnay/[email protected] # dictated by `firefox` to support the `helix` editor, IMPORTANT: adjust etc/msrv-badge.svg as well
       - uses: extractions/setup-just@v1
       - run: just ci-check-msrv

gix-submodule/src/lib.rs

@@ -55,22 +55,20 @@ impl File {
 
         let mut config_to_append = gix_config::File::new(config.meta_owned());
         let mut prev_name = None;
-        let mut section = None;
         for ((module_name, field), values) in values {
             if prev_name.map_or(true, |pn: &BStr| pn != module_name) {
-                section.take();
-                section = Some(
-                    config_to_append
-                        .new_section("submodule", Cow::Owned(module_name.to_owned()))
-                        .expect("all names come from valid configuration, so remain valid"),
-                );
+                config_to_append
+                    .new_section("submodule", Cow::Owned(module_name.to_owned()))
+                    .expect("all names come from valid configuration, so remain valid");
                 prev_name = Some(module_name);
             }
-            let section = section.as_mut().expect("always set at this point");
-            section.push(
-                field.try_into().expect("statically known key"),
-                Some(values.last().expect("at least one value or we wouldn't be here")),
-            );
+            config_to_append
+                .section_mut("submodule", Some(module_name))
+                .expect("always set at this point")
+                .push(
+                    field.try_into().expect("statically known key"),
+                    Some(values.last().expect("at least one value or we wouldn't be here")),
+                );
         }
 
         self.config.append(config_to_append);