add userdiff textconv tests

These tests provide a basic sanity check that textconv'd
files work. The tests try to describe how this configuration
_should_ work; thus some of the tests are marked to expect
failure.

In particular, we fail to actually textconv anything because
the 'diff.foo.binary' config option is not set, which will
be fixed in the next patch.

This also means that some "expect_failure" tests actually
seem to be fixed; in reality, this is just because textconv
is broken and its failure mode happens to make these tests
work.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4030-diff-textconv.sh

@@ -0,0 +1,118 @@
+#!/bin/sh
+
+test_description='diff.*.textconv tests'
+. ./test-lib.sh
+
+find_diff() {
+	sed '1,/^index /d' | sed '/^-- $/,$d'
+}
+
+cat >expect.binary <<'EOF'
+Binary files a/file and b/file differ
+EOF
+
+cat >expect.text <<'EOF'
+--- a/file
++++ b/file
+@@ -1 +1,2 @@
+ 0
++1
+EOF
+
+cat >hexdump <<'EOF'
+#!/bin/sh
+perl -e '$/ = undef; $_ = <>; s/./ord($&)/ge; print $_' "$1"
+EOF
+chmod +x hexdump
+
+test_expect_success 'setup binary file with history' '
+	printf "\\0\\n" >file &&
+	git add file &&
+	git commit -m one &&
+	printf "\\1\\n" >>file &&
+	git add file &&
+	git commit -m two
+'
+
+test_expect_success 'file is considered binary by porcelain' '
+	git diff HEAD^ HEAD >diff &&
+	find_diff <diff >actual &&
+	test_cmp expect.binary actual
+'
+
+test_expect_success 'file is considered binary by plumbing' '
+	git diff-tree -p HEAD^ HEAD >diff &&
+	find_diff <diff >actual &&
+	test_cmp expect.binary actual
+'
+
+test_expect_success 'setup textconv filters' '
+	echo file diff=foo >.gitattributes &&
+	git config diff.foo.textconv "$PWD"/hexdump &&
+	git config diff.fail.textconv false
+'
+
+test_expect_failure 'diff produces text' '
+	git diff HEAD^ HEAD >diff &&
+	find_diff <diff >actual &&
+	test_cmp expect.text actual
+'
+
+test_expect_success 'diff-tree produces binary' '
+	git diff-tree -p HEAD^ HEAD >diff &&
+	find_diff <diff >actual &&
+	test_cmp expect.binary actual
+'
+
+test_expect_failure 'log produces text' '
+	git log -1 -p >log &&
+	find_diff <log >actual &&
+	test_cmp expect.text actual
+'
+
+test_expect_failure 'format-patch produces binary' '
+	git format-patch --no-binary --stdout HEAD^ >patch &&
+	find_diff <patch >actual &&
+	test_cmp expect.binary actual
+'
+
+cat >expect.stat <<'EOF'
+ file |  Bin 2 -> 4 bytes
+ 1 files changed, 0 insertions(+), 0 deletions(-)
+EOF
+test_expect_failure 'diffstat does not run textconv' '
+	echo file diff=fail >.gitattributes &&
+	git diff --stat HEAD^ HEAD >actual &&
+	test_cmp expect.stat actual
+'
+# restore working setup
+echo file diff=foo >.gitattributes
+
+cat >expect.typechange <<'EOF'
+--- a/file
++++ /dev/null
+@@ -1,2 +0,0 @@
+-0
+-1
+diff --git a/file b/file
+new file mode 120000
+index ad8b3d2..67be421
+--- /dev/null
++++ b/file
+@@ -0,0 +1 @@
++frotz
+\ No newline at end of file
+EOF
+# make a symlink the hard way that works on symlink-challenged file systems
+test_expect_failure 'textconv does not act on symlinks' '
+	echo -n frotz > file &&
+	git add file &&
+	git ls-files -s | sed -e s/100644/120000/ |
+		git update-index --index-info &&
+	git commit -m typechange &&
+	git show >diff &&
+	find_diff <diff >actual &&
+	test_cmp expect.typechange actual
+'
+
+test_done