Merge branch 'jn/glossary-revision'

The wording for "revision" in the glossary wanted to say it refers
to "commit (noun) as a concept" but it was badly phrased.

This may need further updates to hint that in contexts where it is
clear, the word may refer to an object name, not necessarily a
commit. But the patch as-is is already an improvement.

* jn/glossary-revision:
  glossary: a revision is just a commit

Documentation/glossary-content.txt

@@ -420,9 +420,7 @@ should not be combined with other pathspec.
 	<<def_merge,merge>> left behind.
 
 [[def_revision]]revision::
-	A particular state of files and directories which was stored in the
+	Synonym for <<def_commit,commit>> (the noun).
-	<<def_object_database,object database>>. It is referenced by a
-	<<def_commit_object,commit object>>.
 
 [[def_rewind]]rewind::
 	To throw away part of the development, i.e. to assign the