From c45bbe3d1c5ff95d7b56fd6b8dd19cd7c9d43aef Mon Sep 17 00:00:00 2001
From: Sylvestre Ledru <sylvestre@debian.org>
Date: Sun, 12 Jan 2025 20:48:33 +0100
Subject: [PATCH] chgrp: add option --from

---
 src/uu/chgrp/src/chgrp.rs   |  24 ++++++-
 tests/by-util/test_chgrp.rs | 130 ++++++++++++++++++++++++++++++++++++
 2 files changed, 153 insertions(+), 1 deletion(-)

diff --git a/src/uu/chgrp/src/chgrp.rs b/src/uu/chgrp/src/chgrp.rs
index fe5aee872..9fc0cb2ff 100644
--- a/src/uu/chgrp/src/chgrp.rs
+++ b/src/uu/chgrp/src/chgrp.rs
@@ -49,11 +49,27 @@ fn parse_gid_and_uid(matches: &ArgMatches) -> UResult<GidUidOwnerFilter> {
             }
         }
     };
+
+    // Handle --from option
+    let filter = if let Some(from_group) = matches.get_one::<String>(options::FROM) {
+        match entries::grp2gid(from_group) {
+            Ok(g) => IfFrom::Group(g),
+            _ => {
+                return Err(USimpleError::new(
+                    1,
+                    format!("invalid group: {}", from_group.quote()),
+                ))
+            }
+        }
+    } else {
+        IfFrom::All
+    };
+
     Ok(GidUidOwnerFilter {
         dest_gid,
         dest_uid: None,
         raw_owner: raw_group,
-        filter: IfFrom::All,
+        filter,
     })
 }
 
@@ -120,6 +136,12 @@ pub fn uu_app() -> Command {
                 .value_hint(clap::ValueHint::FilePath)
                 .help("use RFILE's group rather than specifying GROUP values"),
         )
+        .arg(
+            Arg::new(options::FROM)
+                .long(options::FROM)
+                .value_name("GROUP")
+                .help("change the group only if its current group matches GROUP"),
+        )
         .arg(
             Arg::new(options::RECURSIVE)
                 .short('R')
diff --git a/tests/by-util/test_chgrp.rs b/tests/by-util/test_chgrp.rs
index eca5ba0ed..086f21cb0 100644
--- a/tests/by-util/test_chgrp.rs
+++ b/tests/by-util/test_chgrp.rs
@@ -417,3 +417,133 @@ fn test_traverse_symlinks() {
         );
     }
 }
+
+#[test]
+#[cfg(not(target_vendor = "apple"))]
+fn test_from_option() {
+    use std::os::unix::fs::MetadataExt;
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    let groups = nix::unistd::getgroups().unwrap();
+    // Skip test if we don't have at least two different groups to work with
+    if groups.len() < 2 {
+        return;
+    }
+    let (first_group, second_group) = (groups[0], groups[1]);
+
+    at.touch("test_file");
+    scene
+        .ucmd()
+        .arg(first_group.to_string())
+        .arg("test_file")
+        .succeeds();
+
+    // Test successful group change with --from
+    scene
+        .ucmd()
+        .arg("--from")
+        .arg(first_group.to_string())
+        .arg(second_group.to_string())
+        .arg("test_file")
+        .succeeds()
+        .no_stderr();
+
+    // Verify the group was changed
+    let new_gid = at.plus("test_file").metadata().unwrap().gid();
+    assert_eq!(new_gid, second_group.as_raw());
+
+    scene
+        .ucmd()
+        .arg("--from")
+        .arg(first_group.to_string())
+        .arg(first_group.to_string())
+        .arg("test_file")
+        .succeeds()
+        .no_stderr();
+
+    let unchanged_gid = at.plus("test_file").metadata().unwrap().gid();
+    assert_eq!(unchanged_gid, second_group.as_raw());
+}
+
+#[test]
+#[cfg(not(any(target_os = "android", target_os = "macos")))]
+fn test_from_with_invalid_group() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.touch("test_file");
+    #[cfg(not(target_os = "android"))]
+    let err_msg = "chgrp: invalid user: 'nonexistent_group'\n";
+    #[cfg(target_os = "android")]
+    let err_msg = "chgrp: invalid user: 'staff'\n";
+
+    ucmd.arg("--from")
+        .arg("nonexistent_group")
+        .arg("staff")
+        .arg("test_file")
+        .fails()
+        .stderr_is(err_msg);
+}
+
+#[test]
+#[cfg(not(target_vendor = "apple"))]
+fn test_verbosity_messages() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    let groups = nix::unistd::getgroups().unwrap();
+    // Skip test if we don't have at least one group to work with
+    if groups.is_empty() {
+        return;
+    }
+
+    at.touch("ref_file");
+    at.touch("target_file");
+
+    scene
+        .ucmd()
+        .arg("-v")
+        .arg("--reference=ref_file")
+        .arg("target_file")
+        .succeeds()
+        .stderr_contains("group of 'target_file' retained as ");
+}
+
+#[test]
+#[cfg(not(target_vendor = "apple"))]
+fn test_from_with_reference() {
+    use std::os::unix::fs::MetadataExt;
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    let groups = nix::unistd::getgroups().unwrap();
+    if groups.len() < 2 {
+        return;
+    }
+    let (first_group, second_group) = (groups[0], groups[1]);
+
+    at.touch("ref_file");
+    at.touch("test_file");
+
+    scene
+        .ucmd()
+        .arg(first_group.to_string())
+        .arg("test_file")
+        .succeeds();
+
+    scene
+        .ucmd()
+        .arg(second_group.to_string())
+        .arg("ref_file")
+        .succeeds();
+
+    // Test --from with --reference
+    scene
+        .ucmd()
+        .arg("--from")
+        .arg(first_group.to_string())
+        .arg("--reference=ref_file")
+        .arg("test_file")
+        .succeeds()
+        .no_stderr();
+
+    let new_gid = at.plus("test_file").metadata().unwrap().gid();
+    let ref_gid = at.plus("ref_file").metadata().unwrap().gid();
+    assert_eq!(new_gid, ref_gid);
+}