Revert "Represent git-submodule as nested projects"

This reverts commit 69998b0c6f.
Broke Android's non-gitmodule use case.

Conflicts:
	project.py
	subcmds/sync.py

Change-Id: I68ceeb63d8ee3b939f85a64736bdc81dfa352aed

docs/manifest-format.txt

@@ -45,8 +45,7 @@ following DTD:
     <!ELEMENT manifest-server (EMPTY)>
     <!ATTLIST url              CDATA #REQUIRED>
   
-    <!ELEMENT project (annotation?,
-                       project*)>
+    <!ELEMENT project (annotation?)>
     <!ATTLIST project name     CDATA #REQUIRED>
     <!ATTLIST project path     CDATA #IMPLIED>
     <!ATTLIST project remote   IDREF #IMPLIED>
@@ -153,10 +152,7 @@ Element project
 
 One or more project elements may be specified.  Each element
 describes a single Git repository to be cloned into the repo
-client workspace.  You may specify Git-submodules by creating a
-nested project.  Git-submodules will be automatically
-recognized and inherit their parent's attributes, but those
-may be overridden by an explicitly specified project element.
+client workspace.
 
 Attribute `name`: A unique name for this project.  The project's
 name is appended onto its remote's fetch URL to generate the actual
@@ -167,8 +163,7 @@ URL to configure the Git remote with.  The URL gets formed as:
 where ${remote_fetch} is the remote's fetch attribute and
 ${project_name} is the project's name attribute.  The suffix ".git"
 is always appended as repo assumes the upstream is a forest of
-bare Git repositories.  If the project has a parent element, its
-name will be prefixed by the parent's.
+bare Git repositories.
 
 The project name must match the name Gerrit knows, if Gerrit is
 being used for code reviews.
@@ -176,8 +171,6 @@ being used for code reviews.
 Attribute `path`: An optional path relative to the top directory
 of the repo client where the Git working directory for this project
 should be placed.  If not supplied the project name is used.
-If the project has a parent element, its path will be prefixed
-by the parent's.
 
 Attribute `remote`: Name of a previously defined remote element.
 If not supplied the remote given by the default element is used.
@@ -197,8 +190,6 @@ its name:`name` and path:`path`.  E.g. for
 definition is implicitly in the following manifest groups:
 default, name:monkeys, and path:barrel-of.  If you place a project in the
 group "notdefault", it will not be automatically downloaded by repo.
-If the project has a parent element, the `name` and `path` here
-are the prefixed ones.
 
 Element annotation
 ------------------