Revert "src/usermod.c: Remove optimizations"

This wasn't only an optimization; it also skipped some checks that were
now spuriously triggering errors.  We may be able to get rid of the
optimizations, but that will need more analysis.  For now, let's revert
to a known-good state.

Fixes: 6a8a25d (2025-10-15; "src/usermod.c: Remove optimizations")
Reverts: 6a8a25d (2025-10-15; "src/usermod.c: Remove optimizations")
Closes: <#1509>
Reported-by: Adam Williamson <awilliam@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

Author: alejandro-colomar

src/usermod.c

@@ -1391,6 +1391,48 @@ process_flags(int argc, char **argv, struct option_flags *flags)
 	}
 #endif				/* WITH_SELINUX */
 
+	if (user_newid == user_id) {
+		uflg = false;
+		oflg = false;
+	}
+	if (user_newgid == user_gid) {
+		gflg = false;
+	}
+	if (   (NULL != user_newshell)
+	    && streq(user_newshell, user_shell)) {
+		sflg = false;
+	}
+	if (streq(user_newname, user_name)) {
+		lflg = false;
+	}
+	if (user_newinactive == user_inactive) {
+		fflg = false;
+	}
+	if (user_newexpire == user_expire) {
+		eflg = false;
+	}
+	if (   (NULL != user_newhome)
+	    && streq(user_newhome, user_home)) {
+		dflg = false;
+		mflg = false;
+	}
+	if (   (NULL != user_newcomment)
+	    && streq(user_newcomment, user_comment)) {
+		cflg = false;
+	}
+
+	if (!(Uflg || uflg || sflg || pflg || mflg || Lflg ||
+	      lflg || Gflg || gflg || fflg || eflg || dflg || cflg
+#ifdef ENABLE_SUBIDS
+	      || vflg || Vflg || wflg || Wflg
+#endif				/* ENABLE_SUBIDS */
+#ifdef WITH_SELINUX
+	      || Zflg
+#endif				/* WITH_SELINUX */
+	)) {
+		exit (E_SUCCESS);
+	}
+
 	if (!is_shadow_pwd && (eflg || fflg)) {
 		fprintf (stderr,
 		         _("%s: shadow passwords required for -e and -f\n"),