Merge branch 'po/glossary-around-traversal' into seen

The glossary entries for "commit-graph file" and "reachability
bitmap" have been added.

* po/glossary-around-traversal:
  glossary: add reachability bitmap description
  glossary: add commit graph description
  glossary: add Object DataBase (ODB) abbreviation

Author: gitster

Documentation/glossary-content.txt

@@ -75,6 +75,13 @@ state in the Git history, by creating a new commit representing the current
 state of the <<def_index,index>> and advancing <<def_HEAD,HEAD>>
 to point at the new commit.
 
+[[def_commit_graph]]commit graph::
+	The commit-graph file is a supplemental data structure that
+	accelerates commit graph walks. The existing Object Data Base (ODB)
+	is the definitive commit graph. The "commit-graph" file is stored
+	either in the .git/objects/info directory or in the info directory
+	of an alternate object database.
+
 [[def_commit_object]]commit object::
 	An <<def_object,object>> which contains the information about a
 	particular <<def_revision,revision>>, such as <<def_parent,parents>>, committer,
@@ -257,7 +264,7 @@ This commit is referred to as a "merge commit", or sometimes just a
 	<<def_SHA1,SHA-1>> of its contents. Consequently, an
 	object cannot be changed.
 
-[[def_object_database]]object database::
+[[def_object_database]]object database (ODB)::
 	Stores a set of "objects", and an individual <<def_object,object>> is
 	identified by its <<def_object_name,object name>>. The objects usually
 	live in `$GIT_DIR/objects/`.
@@ -493,6 +500,12 @@ exclude;;
 	<<def_tree_object,trees>> to the trees or <<def_blob_object,blobs>>
 	that they contain.
 
+[[def_reachability_bitmap]]reachability bitmaps::
+	Reachability bitmaps store information about the set of objects in
+	a packfile, or a multi-pack index (MIDX). A repository may have at
+	most one bitmap. The bitmap may belong to either one pack, or the
+	repository's multi-pack index (if it exists).
+
 [[def_rebase]]rebase::
 	To reapply a series of changes from a <<def_branch,branch>> to a
 	different base, and reset the <<def_head,head>> of that branch