From 04b757da79f59b7fc089e542acf32a5597d3d8bc Mon Sep 17 00:00:00 2001
From: Collin Funk <collin.funk1@gmail.com>
Date: Wed, 17 Jun 2026 20:28:38 -0700
Subject: [PATCH] tests: cp,install,mv: check for data loss with just-created
 files

* tests/misc/just-created.sh: New file.
* tests/local.mk (all_tests): Add the test case.
---
 tests/local.mk             |  1 +
 tests/misc/just-created.sh | 98 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 99 insertions(+)
 create mode 100755 tests/misc/just-created.sh

diff --git a/tests/local.mk b/tests/local.mk
index 04f6cb1e36..b56e5dcfb6 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -380,6 +380,7 @@ all_tests =					\
   tests/cksum/md5sum-parallel.sh		\
   tests/join/join.pl				\
   tests/join/join-utf8.sh			\
+  tests/misc/just-created.sh			\
   tests/misc/mknod.sh				\
   tests/nice/nice.sh				\
   tests/nice/nice-fail.sh			\
diff --git a/tests/misc/just-created.sh b/tests/misc/just-created.sh
new file mode 100755
index 0000000000..f2d11b20b5
--- /dev/null
+++ b/tests/misc/just-created.sh
@@ -0,0 +1,98 @@
+#!/bin/sh
+# Test that 'cp', 'mv', and 'install' don't remove just-created files.
+
+# Copyright (C) 2026 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ cp ginstall mv
+
+# Setup the files we expect to see.
+echo a > exp-a || framework_failure_
+echo b > exp-b || framework_failure_
+
+# Setup the initial files and directories for testing.
+reset_files ()
+{
+  rm -rf a b c &&
+  mkdir a b c &&
+  cat exp-a > a/f &&
+  cat exp-b > b/f || framework_failure_
+}
+
+# Check that we don't lose data by overwriting a just-created file.
+for prog in cp ginstall mv; do
+  cat <<EOF >exp || framework_failure_
+$prog: will not overwrite just-created 'c/f' with 'b/f'
+EOF
+  for backup in '' off nil never; do
+    test -n "$backup" && backup=--backup=$backup
+    reset_files
+    returns_ 1 $prog $backup a/f b/f c >out 2>err || fail=1
+    compare /dev/null out || fail=1
+    compare exp err || fail=1
+    # Check if the file specified by the first argument exists.
+    # That should not be the case for 'mv'.
+    if test -f a/f; then
+      test "$prog" != mv || fail=1
+      compare exp-a a/f || fail=1
+    else
+      test $prog != mv && fail=1
+    fi
+    # Check the file specified by the second argument and the
+    # just-created file.
+    compare exp-b b/f || fail=1
+    compare exp-a c/f || fail=1
+    # No backups should be created.
+    set -- c/*
+    test -f "$1" || set --
+    test $# -eq 1 || fail=1
+  done
+done
+
+# With numbered backups there is no data loss if we perform the
+# requested operation.
+for prog in cp ginstall mv; do
+  reset_files
+  for i in $(seq 3); do
+    cat exp-a > a/f || framework_failure_
+    cat exp-b > b/f || framework_failure_
+    $prog --backup=t a/f b/f c >out 2>err || fail=1
+    compare /dev/null out || fail=1
+    compare /dev/null err || fail=1
+    # When using 'mv' both source files should no longer exist.
+    # Otherwise, both files should exist.
+    if test -f a/f; then
+      test $prog != mv || fail=1
+      compare exp-a a/f || fail=1
+      compare exp-b b/f || fail=1
+    else
+      test $prog != mv && fail=1
+      test -f b/f && fail=1
+    fi
+    # Test that the just created file exists.
+    compare exp-b c/f || fail=1
+    for j in $(seq $i); do
+      if test $(($j % 2)) -eq 0; then
+        exp=b
+      else
+        exp=a
+      fi
+      compare exp-$exp c/f.~$j~ || fail=1
+    done
+  done
+done
+
+Exit $fail
-- 
2.47.3