Merge branch 'jk/rev-list-empty-input' into maint

"git log --tag=no-such-tag" showed log starting from HEAD, which
has been fixed---it now shows nothing.

* jk/rev-list-empty-input:
  revision: do not fallback to default when rev_input_given is set
  rev-list: don't show usage when we see empty ref patterns
  revision: add rev_input_given flag
  t6018: flesh out empty input/output rev-list tests

diff --cc builtin/rev-list.c
index e8f5048,1e9cc59..95b4128
--- 1/builtin/rev-list.c
--- 2/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@@ -350,9 -348,10 +350,10 @@@ int cmd_rev_list(int argc, const char *
                /* Only --header was specified */
                revs.commit_format = CMIT_FMT_RAW;
  
 -      if ((!revs.commits &&
 +      if ((!revs.commits && reflog_walk_empty(revs.reflog_info) &&
             (!(revs.tag_objects || revs.tree_objects || revs.blob_objects) &&
-             !revs.pending.nr)) ||
+             !revs.pending.nr) &&
+            !revs.rev_input_given) ||
            revs.diff)
                usage(rev_list_usage);
  

diff --cc revision.c
Simple merge