configparser: address clippy warnings

Summary:
Clippy complains about 3 things:
 - Using raw pointers in a public function that is not declared as unsafe. This
   happens for C exported ones, this feels like a warning, so I haven't changed
   it.
 - Using .map(...).unwrap_or(<default value constructed>). The recommendation
   is to use .unwrap_or_default().
 - Single match instead of if let, the latter makes code much shorter.

Reviewed By: quark-zju

Differential Revision: D20452751

fbshipit-source-id: 8eeff7581c119c651ca41d8117f1f70f15774833

eden/scm/lib/configparser/src/config.rs

@@ -125,7 +125,7 @@ impl ConfigSet {
         self.sections
             .get(section.as_ref())
             .map(|section| section.items.keys().cloned().collect())
-            .unwrap_or(Vec::new())
+            .unwrap_or_default()
     }
 
     /// Get config value for a given config.
@@ -146,13 +146,8 @@ impl ConfigSet {
     pub fn get_sources(&self, section: impl AsRef<str>, name: impl AsRef<str>) -> Vec<ValueSource> {
         self.sections
             .get(section.as_ref())
-            .and_then(|section| {
+            .and_then(|section| section.items.get(name.as_ref()).cloned())
-                section
+            .unwrap_or_default()
-                    .items
-                    .get(name.as_ref())
-                    .map(|values| values.clone())
-            })
-            .unwrap_or(Vec::new())
     }
 
     /// Set a config item directly. `section`, `name` locates the config. `value` is the new value.
@@ -187,7 +182,7 @@ impl ConfigSet {
         if let Some((section, name, value)) = filtered {
             self.sections
                 .entry(section)
-                .or_insert_with(|| Default::default())
+                .or_insert_with(Default::default)
                 .items
                 .entry(name)
                 .or_insert_with(|| Vec::with_capacity(1))
@@ -305,13 +300,10 @@ impl ConfigSet {
         let handle_section = |pair: Pair, section: &mut Text| {
             let pairs = pair.into_inner();
             for pair in pairs {
-                match pair.as_rule() {
+                if let Rule::section_name = pair.as_rule() {
-                    Rule::section_name => {
                     *section = extract(&buf, pair.as_span());
                     return;
                 }
-                    _ => (),
-                }
             }
             unreachable!();
         };
@@ -319,8 +311,7 @@ impl ConfigSet {
         let mut handle_include = |this: &mut ConfigSet, pair: Pair, errors: &mut Vec<Error>| {
             let pairs = pair.into_inner();
             for pair in pairs {
-                match pair.as_rule() {
+                if let Rule::line = pair.as_rule() {
-                    Rule::line => {
                     if !skip_include {
                         let include_path = pair.as_str();
                         let full_include_path =
@@ -328,8 +319,6 @@ impl ConfigSet {
                         this.load_file(&full_include_path, opts, visited, errors);
                     }
                 }
-                    _ => (),
-                }
             }
         };
 
@@ -337,23 +326,14 @@ impl ConfigSet {
             let unset_span = pair.as_span();
             let pairs = pair.into_inner();
             for pair in pairs {
-                match pair.as_rule() {
+                if let Rule::config_name = pair.as_rule() {
-                    Rule::config_name => {
                     let name = extract(&buf, pair.as_span());
                     let location = ValueLocation {
                         path: shared_path.clone(),
                         content: buf.clone(),
                         location: unset_span.start()..unset_span.end(),
                     };
-                        return this.set_internal(
+                    return this.set_internal(section.clone(), name, None, location.into(), opts);
-                            section.clone(),
-                            name,
-                            None,
-                            location.into(),
-                            opts,
-                        );
-                    }
-                    _ => (),
                 }
             }
             unreachable!();

eden/scm/lib/configparser/src/hg.rs

@@ -585,7 +585,7 @@ fn parse_list_internal(value: &str) -> Vec<String> {
                             Some(last) => {
                                 if last.is_empty() {
                                     1
-                                } else if last.ends_with("\\") {
+                                } else if last.ends_with('\\') {
                                     2
                                 } else {
                                     3