Add the ability to add additional patches when building the Windows release

Author: embray

CHANGES.md

@@ -1,10 +1,15 @@
 Changelog for the Windows Installer
 ===================================
 
-0.4.3 (unreleased)
+0.4.3 (2019-04-18)
 ------------------
 
-* Nothing changed yet.
+* Not a change to the installer itself but to the build toolchain, allowing
+  version-specific patches to be applied after a Sage release.  From
+  time-to-time critical bugs are found and fixed in Sage only after an
+  official release.  And Sage's development process is not quick enough
+  about making new releases.  So we add the ability to include post-release
+  patches as needed.
 
 
 0.4.2 (2019-02-11)

Makefile

@@ -37,6 +37,7 @@ cygwin-runtime-extras=$(STAMPS)/cygwin-runtime-extras-$(SAGE_VERSION)-$(ARCH)
 ###############################################################################
 
 # Resource paths
+PATCHES=patches
 CYGWIN_EXTRAS=cygwin_extras
 RESOURCES=resources
 DOT_SAGE=dot_sage
@@ -218,6 +219,13 @@ $(SAGE_CONFIGURE): | $(SAGE_ROOT_BUILD)
 $(SAGE_ROOT_BUILD): $(cygwin-build)
 	[ -d $(dir $(SAGE_ROOT_BUILD)) ] || mkdir $(dir $(SAGE_ROOT_BUILD))
 	$(SUBCYG) "$(ENV_BUILD_DIR)" "(cd /opt && git clone --single-branch --branch $(SAGE_BRANCH) $(SAGE_GIT) $(SAGE_ROOT))"
+	# Apply patches
+	if [ -d $(PATCHES)/$(SAGE_BRANCH) ]; then \
+		for patch in $(PATCHES)/$(SAGE_BRANCH)/*.patch; do \
+		    patch="$$(pwd)/$$patch"; \
+			(cd $(SAGE_ROOT_BUILD) && patch -p1 < $$patch); \
+		done; \
+	fi
 
 
 $(CYGWIN_SETUP): | $(DOWNLOAD)