[PATCH] read-tree: "read-tree -m --empty" does not make sense

fb1bb965 ("read-tree: deprecate syntax without tree-ish args",
2010-09-10) wanted to deprecate "git read-tree" without any tree,
which used to be the way to empty the index, and encourage use of
"git read-tree --empty" instead.  

However, when used with "-m", "--empty" does not make any sense,
either, simply because merging 0 trees will result in a different
error anyway.

Omit the deprecation warning and let the code to emit real error
message diagnose the error.

Signed-off-by: Junio C Hamano <redacted>
---

    Junio C Hamano [off-list ref] writes:

    > Jean-Noel Avila [off-list ref] writes:
    >
    >> "git read-tree -m" requires a tree argument to name the tree to be
    >> merged in.  Git uses a cutesy error message to say so and why:
    >>
    >>     $ git read-tree -m
    >>     warning: read-tree: emptying the index with no arguments is
    >>     deprecated; use --empty
    >>     fatal: just how do you expect me to merge 0 trees?
    >>     $ git read-tree -m --empty
    >>     fatal: just how do you expect me to merge 0 trees?
    >
    > This shows another issue.  The "emptying ... is deprecated" message
    > shouldn't be given when -m is present.
    >
    > I am not saying that that needs to be fixed by you and/or as a part
    > of this patch.  Just something I noticed while reviewing the patch.

 builtin/read-tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/read-tree.c b/builtin/read-tree.c
index 23e212ee8c..284de743c3 100644
--- a/builtin/read-tree.c
+++ b/builtin/read-tree.c

@@ -210,7 +210,7 @@ int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
 			die("failed to unpack tree object %s", arg);
 		stage++;
 	}
-	if (nr_trees == 0 && !read_empty)
+	if (!nr_trees && !read_empty && !opts.merge)
 		warning("read-tree: emptying the index with no arguments is deprecated; use --empty");
 	else if (nr_trees > 0 && read_empty)
 		die("passing trees as arguments contradicts --empty");

-- 
2.13.0-336-gf73534b083