[PATCH v3 1/3] Demonstrate a bug in --word-diff where diff.*.wordregex is "sticky"

[Johannes Sixt <j6t@kdbg.org>]

The test case applies a custom wordRegex to one file in a diff, and expects
that the default word splitting applies to the second file in the diff.
But the custom wordRegex is also incorrectly used for the second file.

Helped-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
---
Changes in this round, where I do not resend 2/3 and 3/3:

- Use test_unconfig.
- Use compare_diff_patch to check the result.
- Fix a broken && chain at the end of the last test.
- Name the files a.tex and z.tex as per your suggestion.

 t/t4034-diff-words.sh |   36 ++++++++++++++++++++++++++++++++++++
 1 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/t/t4034-diff-words.sh b/t/t4034-diff-words.sh
index 5c20121..9e9643e 100755
--- a/t/t4034-diff-words.sh
+++ b/t/t4034-diff-words.sh
@@ -3,6 +3,7 @@
 test_description='word diff colors'
 
 . ./test-lib.sh
+. "$TEST_DIRECTORY"/diff-lib.sh
 
 cat >pre.simple <<-\EOF
 	h(4)
@@ -293,6 +294,10 @@ test_expect_success '--word-diff=none' '
 	word_diff --word-diff=plain --word-diff=none
 '
 
+test_expect_success 'unset default driver' '
+	test_unconfig diff.wordregex
+'
+
 test_language_driver bibtex
 test_language_driver cpp
 test_language_driver csharp
@@ -348,4 +353,35 @@ test_expect_success 'word-diff with no newline at EOF' '
 	word_diff --word-diff=plain
 '
 
+test_expect_success 'setup history with two files' '
+	echo "a b; c" >a.tex &&
+	echo "a b; c" >z.tex &&
+	git add a.tex z.tex &&
+	git commit -minitial &&
+
+	# modify both
+	echo "a bx; c" >a.tex &&
+	echo "a bx; c" >z.tex &&
+	git commit -mmodified -a
+'
+
+test_expect_failure 'wordRegex for the first file does not apply to the second' '
+	echo "a.tex diff=tex" >.gitattributes &&
+	git config diff.tex.wordRegex "[a-z]+|." &&
+	cat >expect <<-\EOF &&
+		diff --git a/a.tex b/a.tex
+		--- a/a.tex
+		+++ b/a.tex
+		@@ -1 +1 @@
+		a [-b-]{+bx+}; c
+		diff --git a/z.tex b/z.tex
+		--- a/z.tex
+		+++ b/z.tex
+		@@ -1 +1 @@
+		a [-b;-]{+bx;+} c
+	EOF
+	git diff --word-diff HEAD~ >actual &&
+	compare_diff_patch expect actual
+'
+
 test_done
-- 
1.7.8.216.g2e426