switch: reject "do nothing" case

"git checkout" can be executed without any arguments. What it does is
not exactly great: it switches from HEAD to HEAD and shows worktree
modification as a side effect.

Make switch reject this case. Just use "git status" if you want
that side effect. For switch, you have to either

- really switch a branch
- (explicitly) detach from the current branch
- create a new branch

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 0584dc484d0203866fa9f84fcb6b61409baeeefd..e9dfe38d69d46b11b271995a7d68cf18db4795a1 100644 (file)
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -55,6 +55,7 @@ struct checkout_opts {
        int no_dwim_new_local_branch;
        int discard_changes;
        int accept_pathspec;
+       int switch_branch_doing_nothing_is_ok;
 
        /*
         * If new checkout options are added, skip_merge_working_tree
@@ -1338,6 +1339,12 @@ static int checkout_branch(struct checkout_opts *opts,
                die(_("Cannot switch branch to a non-commit '%s'"),
                    new_branch_info->name);
 
+       if (!opts->switch_branch_doing_nothing_is_ok &&
+           !new_branch_info->name &&
+           !opts->new_branch &&
+           !opts->force_detach)
+               die(_("missing branch or commit argument"));
+
        if (new_branch_info->path && !opts->force_detach && !opts->new_branch &&
            !opts->ignore_other_worktrees) {
                int flag;
@@ -1593,6 +1600,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 
        memset(&opts, 0, sizeof(opts));
        opts.no_dwim_new_local_branch = 0;
+       opts.switch_branch_doing_nothing_is_ok = 1;
        opts.accept_pathspec = 1;
 
        options = parse_options_dup(checkout_options);
@@ -1624,6 +1632,7 @@ int cmd_switch(int argc, const char **argv, const char *prefix)
        memset(&opts, 0, sizeof(opts));
        opts.no_dwim_new_local_branch = 0;
        opts.accept_pathspec = 0;
+       opts.switch_branch_doing_nothing_is_ok = 0;
 
        options = parse_options_dup(switch_options);
        options = add_common_options(&opts, options);