Avoid using #[cfg] on multiple individual function arguments

Attaching #[cfg] to individual arguments makes it look like the function
has five conditionally present arguments, and doesn't make it
immediately apparent that the first two are for the first argument and
the last three are for the second argument.

Split them into separate `let` statements for clarity.

In the process, factor out the common `.try_into().ok()?` from each.

gix-index/src/fs.rs

@@ -54,17 +54,21 @@ impl Metadata {
     pub fn modified(&self) -> Option<SystemTime> {
         #[cfg(not(windows))]
         {
+            #[cfg(not(target_os = "aix"))]
+            let seconds = self.0.st_mtime;
+            #[cfg(target_os = "aix")]
+            let seconds = self.0.st_mtim.tv_sec;
+
+            #[cfg(not(any(target_os = "netbsd", target_os = "aix")))]
+            let nanoseconds = self.0.st_mtime_nsec;
+            #[cfg(target_os = "netbsd")]
+            let nanoseconds = self.0.st_mtimensec;
+            #[cfg(target_os = "aix")]
+            let nanoseconds = self.0.st_mtim.tv_nsec;
+
             Some(system_time_from_secs_nanos(
-                #[cfg(not(target_os = "aix"))]
-                self.0.st_mtime.try_into().ok()?,
-                #[cfg(target_os = "aix")]
-                self.0.st_mtim.tv_sec.try_into().ok()?,
-                #[cfg(not(any(target_os = "netbsd", target_os = "aix")))]
-                self.0.st_mtime_nsec.try_into().ok()?,
-                #[cfg(target_os = "netbsd")]
-                self.0.st_mtimensec.try_into().ok()?,
-                #[cfg(target_os = "aix")]
-                self.0.st_mtim.tv_nsec.try_into().ok()?,
+                seconds.try_into().ok()?,
+                nanoseconds.try_into().ok()?,
             ))
         }
         #[cfg(windows)]
@@ -78,17 +82,21 @@ impl Metadata {
     pub fn created(&self) -> Option<SystemTime> {
         #[cfg(not(windows))]
         {
+            #[cfg(not(target_os = "aix"))]
+            let seconds = self.0.st_ctime;
+            #[cfg(target_os = "aix")]
+            let seconds = self.0.st_ctim.tv_sec;
+
+            #[cfg(not(any(target_os = "netbsd", target_os = "aix")))]
+            let nanoseconds = self.0.st_ctime_nsec;
+            #[cfg(target_os = "netbsd")]
+            let nanoseconds = self.0.st_ctimensec;
+            #[cfg(target_os = "aix")]
+            let nanoseconds = self.0.st_ctim.tv_nsec;
+
             Some(system_time_from_secs_nanos(
-                #[cfg(not(target_os = "aix"))]
-                self.0.st_ctime.try_into().ok()?,
-                #[cfg(target_os = "aix")]
-                self.0.st_ctim.tv_sec.try_into().ok()?,
-                #[cfg(not(any(target_os = "netbsd", target_os = "aix")))]
-                self.0.st_ctime_nsec.try_into().ok()?,
-                #[cfg(target_os = "netbsd")]
-                self.0.st_ctimensec.try_into().ok()?,
-                #[cfg(target_os = "aix")]
-                self.0.st_ctim.tv_nsec.try_into().ok()?,
+                seconds.try_into().ok()?,
+                nanoseconds.try_into().ok()?,
             ))
         }
         #[cfg(windows)]