Merge branch 'jc/dotdot-is-parent-directory' into maint-1.7.11

"git log .." errored out saying it is both rev range and a path when
there is no disambiguating "--" is on the command line.  Update the
command line parser to interpret ".." as a path in such a case.

* jc/dotdot-is-parent-directory:
specifying ranges: we did not mean to make ".." an empty set

diff --combined revision.c
index 6d21ac7ee1ccb1aa014dc977955d7fce6d92ede2,457868d647378e4b3249f7c3ecae6697bc1ddc04..72104962d36b9672fd9dfc6ec850c99ccfc3803c
--- 1/revision.c
--- 2/revision.c
+++ b/revision.c
@@@ -345,7 -345,6 +345,7 @@@ static int tree_difference = REV_TREE_S
  static void file_add_remove(struct diff_options *options,
                    int addremove, unsigned mode,
                    const unsigned char *sha1,
 +                  int sha1_valid,
                    const char *fullpath, unsigned dirty_submodule)
  {
        int diff = addremove == '+' ? REV_TREE_NEW : REV_TREE_OLD;
@@@ -359,7 -358,6 +359,7 @@@ static void file_change(struct diff_opt
                 unsigned old_mode, unsigned new_mode,
                 const unsigned char *old_sha1,
                 const unsigned char *new_sha1,
 +               int old_sha1_valid, int new_sha1_valid,
                 const char *fullpath,
                 unsigned old_dirty_submodule, unsigned new_dirty_submodule)
  {
@@@ -1134,15 -1132,27 +1134,27 @@@ int handle_revision_arg(const char *arg
                const char *this = arg;
                int symmetric = *next == '.';
                unsigned int flags_exclude = flags ^ UNINTERESTING;
+               static const char head_by_default[] = "HEAD";
                unsigned int a_flags;
  
                *dotdot = 0;
                next += symmetric;
  
                if (!*next)
-                       next = "HEAD";
+                       next = head_by_default;
                if (dotdot == arg)
-                       this = "HEAD";
+                       this = head_by_default;
+               if (this == head_by_default && next == head_by_default &&
+                   !symmetric) {
+                       /*
+                        * Just ".."?  That is not a range but the
+                        * pathspec for the parent directory.
+                        */
+                       if (!cant_be_filename) {
+                               *dotdot = '.';
+                               return -1;
+                       }
+               }
                if (!get_sha1(this, from_sha1) &&
                    !get_sha1(next, sha1)) {
                        struct commit *a, *b;
@@@ -1855,7 -1865,8 +1867,7 @@@ int setup_revisions(int argc, const cha
        if (revs->combine_merges)
                revs->ignore_merges = 0;
        revs->diffopt.abbrev = revs->abbrev;
 -      if (diff_setup_done(&revs->diffopt) < 0)
 -              die("diff_setup_done failed");
 +      diff_setup_done(&revs->diffopt);
  
        compile_grep_patterns(&revs->grep_filter);