TO-RESOLVE

This reflects the merge conflict resolutions with the previous merge
commit as rebased from Git for Windows' `master` on top of upstream.
Once the conflicting patch series make it to an official Git version,
Git for Windows' `master` will need to take these merge conflict
resolutions in a more permanent way.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

builtin/difftool.c

@@ -723,11 +723,15 @@ int cmd_difftool(int argc, const char **argv, const char *prefix)
 	if (!no_index && !startup_info->have_repository)
 		die(_("difftool requires worktree or --no-index"));
 
+	if (use_gui_tool + !!difftool_cmd + !!extcmd > 1)
+		die(_("--gui, --tool and --extcmd are mutually exclusive"));
+
 	if (!no_index){
 		setup_work_tree();
 		setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
 		setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
-	}
+	} else if (dir_diff)
+		die(_("--dir-diff is incompatible with --no-index"));
 
 	if (use_gui_tool)
 		setenv("GIT_MERGETOOL_GUI", "true", 1);

t/t7800-difftool.sh

@@ -726,9 +726,17 @@ test_expect_success 'outside worktree' '
 	echo 2 >2 &&
 	test_expect_code 1 nongit git \
 		-c diff.tool=echo -c difftool.echo.cmd="echo \$LOCAL \$REMOTE" \
-		difftool --no-prompt --no-index --ext-diff ../1 ../2 >actual &&
+		difftool --no-prompt --no-index ../1 ../2 >actual &&
 	echo "../1 ../2" >expect &&
 	test_cmp expect actual
 '
 
+test_expect_success 'difftool --gui, --tool and --extcmd are exclusive' '
+	difftool_test_setup &&
+	test_must_fail git difftool --gui --tool=test-tool &&
+	test_must_fail git difftool --gui --extcmd=cat &&
+	test_must_fail git difftool --tool=test-tool --extcmd=cat &&
+	test_must_fail git difftool --gui --tool=test-tool --extcmd=cat
+'
+
 test_done