pack-objects (mingw): demonstrate a segmentation fault with large deltas

There is a problem in the way 9ac3f0e5b3 (pack-objects: fix
performance issues on packing large deltas, 2018-07-22) initializes that
mutex in the `packing_data` struct. The problem manifests in a
segmentation fault on Windows, when a mutex (AKA critical section) is
accessed without being initialized. (With pthreads, you apparently do
not really have to initialize them?)

This was reported in https://github.com/git-for-windows/git/issues/1839.

Signed-off-by: Doug Kelly <dougk.ff7@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

t/t7422-submodule-long-path.sh

@@ -0,0 +1,105 @@
+#!/bin/sh
+#
+# Copyright (c) 2013 Doug Kelly
+#
+
+test_description='Test submodules with a path near PATH_MAX
+
+This test verifies that "git submodule" initialization, update and clones work, including with recursive submodules and paths approaching PATH_MAX (260 characters on Windows)
+'
+
+TEST_NO_CREATE_REPO=1
+. ./test-lib.sh
+
+longpath=""
+for (( i=0; i<4; i++ )); do
+	longpath="0123456789abcdefghijklmnopqrstuvwxyz$longpath"
+done
+# Pick a substring maximum of 90 characters
+# This should be good, since we'll add on a lot for temp directories
+longpath=${longpath:0:90}; export longpath
+
+test_expect_failure 'submodule with a long path' '
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=long init --bare remote &&
+	test_create_repo bundle1 &&
+	(
+		cd bundle1 &&
+		test_commit "shoot" &&
+		git rev-parse --verify HEAD >../expect
+	) &&
+	mkdir home &&
+	(
+		cd home &&
+		git clone ../remote test &&
+		cd test &&
+		git checkout -B long &&
+		git submodule add ../bundle1 $longpath &&
+		test_commit "sogood" &&
+		(
+			cd $longpath &&
+			git rev-parse --verify HEAD >actual &&
+			test_cmp ../../../expect actual
+		) &&
+		git push origin long
+	) &&
+	mkdir home2 &&
+	(
+		cd home2 &&
+		git clone ../remote test &&
+		cd test &&
+		git checkout long &&
+		git submodule update --init &&
+		(
+			cd $longpath &&
+			git rev-parse --verify HEAD >actual &&
+			test_cmp ../../../expect actual
+		)
+	)
+'
+
+test_expect_failure 'recursive submodule with a long path' '
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
+	git -c init.defaultBranch=long init --bare super &&
+	test_create_repo child &&
+	(
+		cd child &&
+		test_commit "shoot" &&
+		git rev-parse --verify HEAD >../expect
+	) &&
+	test_create_repo parent &&
+	(
+		cd parent &&
+		git submodule add ../child $longpath &&
+		test_commit "aim"
+	) &&
+	mkdir home3 &&
+	(
+		cd home3 &&
+		git clone ../super test &&
+		cd test &&
+		git checkout -B long &&
+		git submodule add ../parent foo &&
+		git submodule update --init --recursive &&
+		test_commit "sogood" &&
+		(
+			cd foo/$longpath &&
+			git rev-parse --verify HEAD >actual &&
+			test_cmp ../../../../expect actual
+		) &&
+		git push origin long
+	) &&
+	mkdir home4 &&
+	(
+		cd home4 &&
+		git clone ../super test --recursive &&
+		(
+			cd test/foo/$longpath &&
+			git rev-parse --verify HEAD >actual &&
+			test_cmp ../../../../expect actual
+		)
+	)
+'
+unset longpath
+
+test_done