test: add machinery to download and verify databases

Note that it is intentional that the checksum file is not
downloaded. The intent is to check those into git.

Makefile

@@ -5,7 +5,8 @@ all:
 # List all subdirectories here. Each contains its own Makefile.local.
 # Use of '=', without '+=', seems to be required for out-of-tree
 # builds to work.
-subdirs = compat completion doc emacs lib parse-time-string performance-test util test
+subdirs = compat completion doc emacs lib parse-time-string	\
+	performance-test util test test/test-databases
 
 # We make all targets depend on the Makefiles themselves.
 global_deps = Makefile Makefile.config Makefile.local \

test/README

@@ -64,6 +64,14 @@ The following command-line options are available when running tests:
 	Pointing this argument at a tmpfs filesystem can improve the
 	speed of the test suite for some users.
 
+Certain tests require precomputed databases to complete. You can fetch these
+databases with
+
+	make download-test-databases
+
+If you do not download the test databases, the relevant tests will be
+skipped.
+
 When invoking the test suite via "make test" any of the above options
 can be specified as follows:
 

test/T530-upgrade.sh

@@ -7,7 +7,7 @@ dbtarball=database-v1.tar.xz
 
 # XXX: Accomplish the same with test lib helpers
 if [ ! -e ${TEST_DIRECTORY}/test-databases/${dbtarball} ]; then
-    test_subtest_missing_external_prereq_["${dbtarball}"]=t
+    test_subtest_missing_external_prereq_["${dbtarball} - fetch with 'make download-test-databases'"]=t
 fi
 
 test_expect_success \

test/test-databases/Makefile

@@ -0,0 +1,7 @@
+# See Makefile.local for the list of files to be compiled in this
+# directory.
+all:
+	$(MAKE) -C ../.. all
+
+.DEFAULT:
+	$(MAKE) -C ../.. $@

test/test-databases/Makefile.local

@@ -0,0 +1,14 @@
+# -*- makefile -*-
+
+TEST_DATABASE_MIRROR=http://notmuchmail.org/releases/test-databases
+
+dir := test/test-databases
+
+test_databases := $(dir)/database-v1.tar.xz
+
+%.tar.xz:
+	wget -nv -O $@ ${TEST_DATABASE_MIRROR}/$(notdir $@);
+
+download-test-databases: ${test_databases}
+
+DISTCLEAN := $(DISTCLEAN) ${test_databases}