Fix '~' user source expansion for --copyout

mock/py/mock.py

@@ -1006,7 +1006,9 @@ def run_command(options, args, config_opts, commands, buildroot):
             dest = args[-1]
             sources = []
             for arg in args[:-1]:
-                matches = glob.glob(buildroot.make_chroot_path(arg.replace('~', buildroot.homedir)))
+                with util.env_var_override("HOME", buildroot.homedir):
+                    arg = os.path.expanduser(arg)
+                matches = glob.glob(buildroot.make_chroot_path(arg))
                 if not matches:
                     log.critical("%s not found", arg)
                     return 50

mock/py/mockbuild/util.py

@@ -1079,3 +1079,22 @@ def nullcontext():
     Python 3.6+ compatible because of EL 8
     """
     yield None
+
+@contextlib.contextmanager
+def env_var_override(name, value):
+    """
+    Temporary set environment variable NAME to VALUE, revert to the previous
+    state.
+    """
+
+    oldval = None
+    if name in os.environ:
+        oldval = os.environ[name]
+
+    os.environ[name] = value
+    yield
+
+    if oldval is None:
+        del os.environ[name]
+    else:
+        os.environ[name] = oldval

releng/release-notes-next/expanduser-with-copyout.bugfix

@@ -0,0 +1,4 @@
+Previous versions of Mock mistakenly expanded every `~` occurrence
+(tilde character) in the specified source path with `--copyout`.  So
+files `~/foo~bar.txt` were searched on path `/builddir/foo/builddirbar.txt`
+instead of just `/builddir/foo~bar.txt`.  Fixes [rhbz#2239035][].