changed naming of variables and added a comment

Author: asder8215

library/std/src/fs.rs

@@ -3334,16 +3334,19 @@ impl DirBuilder {
         }
 
         let ancestors = path.ancestors();
-        let mut uncreated_dir_ctr = 0;
+        let mut uncreated_dirs = 0;
 
         for ancestor in ancestors {
+            // for relative paths like "foo/bar", the parent of
+            // "foo" will be "" which there's no need to invoke
+            // a mkdir syscall on
             if ancestor == Path::new("") {
                 break;
             }
 
             match self.inner.mkdir(ancestor) {
                 Ok(()) => break,
-                Err(e) if e.kind() == io::ErrorKind::NotFound => uncreated_dir_ctr += 1,
+                Err(e) if e.kind() == io::ErrorKind::NotFound => uncreated_dirs += 1,
                 // we check if the err is AlreadyExists for two reasons
                 //    - in case the path exists as a *file*
                 //    - and to avoid calls to .is_dir() in case of other errs
@@ -3354,10 +3357,10 @@ impl DirBuilder {
         }
 
         // collect only the uncreated directories w/o letting the vec resize
-        let mut uncreated_dirs = Vec::with_capacity(uncreated_dir_ctr);
-        uncreated_dirs.extend(ancestors.take(uncreated_dir_ctr));
+        let mut uncreated_dirs_vec = Vec::with_capacity(uncreated_dirs);
+        uncreated_dirs_vec.extend(ancestors.take(uncreated_dirs));
 
-        for uncreated_dir in uncreated_dirs.iter().rev() {
+        for uncreated_dir in uncreated_dirs_vec.iter().rev() {
             if let Err(e) = self.inner.mkdir(uncreated_dir) {
                 if e.kind() != io::ErrorKind::AlreadyExists || !uncreated_dir.is_dir() {
                     return Err(e);