python-pip: revamp installation procedure (use setuptools machinery)

PIP's installation procedure was too complicated, requiring obscure
postinstall and prerm scripts to move files created by setup procedure.
But since setuptools is required anyway, it's better to use a special
flag created for the purpose of package creation. Resulting directory
structure is flatter and unnecessary files that had to be moved by
prerm/postinstall scripts are not created anymore.

Signed-off-by: Jan Čermák <jan.cermak@nic.cz>

lang/python-pip/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=python-pip
 PKG_VERSION:=7.1.0
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=pip-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://pypi.python.org/packages/source/p/pip/
@@ -36,34 +36,14 @@ endef
 
 define Build/Compile
 	$(call Build/Compile/PyMod,,\
-		install --prefix="$(PKG_INSTALL_DIR)/usr" \
+		install --root="$(PKG_INSTALL_DIR)" --prefix="/usr" \
+		--single-version-externally-managed \
 	)
 endef
 
-PYTHON_PIP_PKG_DIR:=$(PYTHON_PKG_DIR)/pip-$(PKG_VERSION)-py$(PYTHON_VERSION).egg/pip
 define PyPackage/python-pip/filespec
 +|$(PYTHON_PKG_DIR)
--|$(PYTHON_PIP_PKG_DIR)/_vendor/distlib/*.exe
-endef
-
-# Backup these files, so that they do not clash with python-setuptools
-# If we install python-pip python-setuptools, we want these to be replaced,
-# since python-pip replaces python-setuptools (when installed)
-define Package/python-pip/preinst
-#!/bin/sh
-cd "$${IPKG_INSTROOT}$(PYTHON_PKG_DIR)"
-mv -f easy-install.pth easy-install.pth.old
-mv -f site.py site.py.old
-exit 0
-endef
-
-# And put them back on remove
-define Package/python-pip/postrm
-#!/bin/sh
-cd "$${IPKG_INSTROOT}$(PYTHON_PKG_DIR)"
-mv -f easy-install.pth.old easy-install.pth
-mv -f site.py.old site.py
-exit 0
+-|$(PYTHON_PKG_DIR)/pip/_vendor/distlib/*.exe
 endef
 
 define PyPackage/python-pip/install