From cebf1f09dff0925b5056bc49c5c43751a168dc30 Mon Sep 17 00:00:00 2001
From: Jeong YunWon <jeong@youknowone.org>
Date: Thu, 10 Jun 2021 01:54:10 +0900
Subject: [PATCH 1/2] get_groups_gnu sort with rotate_right

---
 src/uucore/src/lib/features/entries.rs | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/uucore/src/lib/features/entries.rs b/src/uucore/src/lib/features/entries.rs
index b94abbe4f..75bf245e4 100644
--- a/src/uucore/src/lib/features/entries.rs
+++ b/src/uucore/src/lib/features/entries.rs
@@ -95,15 +95,18 @@ pub fn get_groups() -> IOResult<Vec<gid_t>> {
 /// history of a process and its parents could affect the details of
 /// the result.)
 pub fn get_groups_gnu(arg_id: Option<u32>) -> IOResult<Vec<gid_t>> {
-    let mut groups = get_groups()?;
+    let groups = get_groups()?;
     let egid = arg_id.unwrap_or_else(crate::features::process::getegid);
-    if !groups.is_empty() && *groups.first().unwrap() == egid {
-        return Ok(groups);
-    } else if let Some(index) = groups.iter().position(|&x| x == egid) {
-        groups.remove(index);
+    Ok(sort_groups(groups, egid))
+}
+
+fn sort_groups(mut groups: Vec<gid_t>, egid: gid_t) -> Vec<gid_t> {
+    if let Some(index) = groups.iter().position(|&x| x == egid) {
+        groups[..index + 1].rotate_right(1);
+    } else {
+        groups.insert(0, egid);
     }
-    groups.insert(0, egid);
-    Ok(groups)
+    groups
 }
 
 #[derive(Copy, Clone)]
@@ -308,6 +311,15 @@ pub fn grp2gid(name: &str) -> IOResult<gid_t> {
 mod test {
     use super::*;
 
+    #[test]
+    fn test_sort_groups() {
+        assert_eq!(sort_groups(vec![1, 2, 3], 4), vec![4, 1, 2, 3]);
+        assert_eq!(sort_groups(vec![1, 2, 3], 3), vec![3, 1, 2]);
+        assert_eq!(sort_groups(vec![1, 2, 3], 2), vec![2, 1, 3]);
+        assert_eq!(sort_groups(vec![1, 2, 3], 1), vec![1, 2, 3]);
+        assert_eq!(sort_groups(vec![1, 2, 3], 0), vec![0, 1, 2, 3]);
+    }
+
     #[test]
     fn test_entries_get_groups_gnu() {
         if let Ok(mut groups) = get_groups() {

From 23f655e2a514ee2730601f7ac184d84763e8e07e Mon Sep 17 00:00:00 2001
From: Jeong YunWon <youknowone@users.noreply.github.com>
Date: Thu, 10 Jun 2021 11:15:01 +0900
Subject: [PATCH 2/2] Use inclusive range

Co-authored-by: Michael Debertol <michael.debertol@gmail.com>
---
 src/uucore/src/lib/features/entries.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/uucore/src/lib/features/entries.rs b/src/uucore/src/lib/features/entries.rs
index 75bf245e4..7d8c78a2f 100644
--- a/src/uucore/src/lib/features/entries.rs
+++ b/src/uucore/src/lib/features/entries.rs
@@ -102,7 +102,7 @@ pub fn get_groups_gnu(arg_id: Option<u32>) -> IOResult<Vec<gid_t>> {
 
 fn sort_groups(mut groups: Vec<gid_t>, egid: gid_t) -> Vec<gid_t> {
     if let Some(index) = groups.iter().position(|&x| x == egid) {
-        groups[..index + 1].rotate_right(1);
+        groups[..=index].rotate_right(1);
     } else {
         groups.insert(0, egid);
     }