glossary: more precise definition of tree-ish (a.k.a. treeish)

A tree-ish isn't a ref.  Also, mention dereferencing, and that a
commit dereferences to a tree, to support gitrevisions(7) and
rev-parse's error messages.

Signed-off-by: Richard Hansen <rhansen@bbn.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/glossary-content.txt b/Documentation/glossary-content.txt
index 47e901ece8b19288cd4eb8ca3a5dcfeecb25691a..3466ce9129ba8decaa9d8dcf7e83e5898d0b3aea 100644 (file)
--- a/Documentation/glossary-content.txt
+++ b/Documentation/glossary-content.txt
@@ -499,9 +499,18 @@ should not be combined with other pathspec.
        <<def_tree,tree>> is equivalent to a <<def_directory,directory>>.
 
 [[def_tree-ish]]tree-ish (also treeish)::
-       A <<def_ref,ref>> pointing to either a <<def_commit_object,commit
-       object>>, a <<def_tree_object,tree object>>, or a <<def_tag_object,tag
-       object>> pointing to a tag or commit or tree object.
+       A <<def_tree_object,tree object>> or an <<def_object,object>>
+       that can be recursively dereferenced to a tree object.
+       Dereferencing a <<def_commit_object,commit object>> yields the
+       tree object corresponding to the <<def_revision,revision>>'s
+       top <<def_directory,directory>>.
+       The following are all tree-ishes:
+       a <<def_commit-ish,commit-ish>>,
+       a tree object,
+       a <<def_tag_object,tag object>> that points to a tree object,
+       a tag object that points to a tag object that points to a tree
+       object,
+       etc.
 
 [[def_unmerged_index]]unmerged index::
        An <<def_index,index>> which contains unmerged