thodg/libgit2

diff --git a/src/diff_driver.c b/src/diff_driver.c
index dcd74ad..169f7b0 100644
--- a/src/diff_driver.c
+++ b/src/diff_driver.c
@@ -52,10 +52,38 @@ typedef struct {
 	int flags;
 } git_diff_driver_definition;
 
+#define WORD_DEFAULT "|[^[:space:]]|[\xc0-\xff][\x80-\xbf]+"
+
+/* builtin driver definition macros have same signature as in core git
+ * userdiff.c so that the data can be extracted verbatim
+ */
+#define PATTERNS(NAME, FN_PATS, WORD_PAT) \
+	{ NAME, FN_PATS, WORD_PAT WORD_DEFAULT, 0 }
+#define IPATTERN(NAME, FN_PATS, WORD_PAT) \
+	{ NAME, FN_PATS, WORD_PAT WORD_DEFAULT, REG_ICASE }
+
 static git_diff_driver_definition builtin_defs[] = {
-	{ "html", "^[ \t]*(<h[1-8]([ \t][^>]*)?>.*)$", "[^<> \t]+", REG_ICASE },
+PATTERNS("html", "^[ \t]*(<[Hh][1-6][ \t].*>.*)$",
+	 "[^<>= \t]+"),
+PATTERNS("java",
+	 "!^[ \t]*(catch|do|for|if|instanceof|new|return|switch|throw|while)\n"
+	 "^[ \t]*(([A-Za-z_][A-Za-z_0-9]*[ \t]+)+[A-Za-z_][A-Za-z_0-9]*[ \t]*\\([^;]*)$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.e]+[fFlL]?|0[xXbB]?[0-9a-fA-F]+[lL]?"
+	 "|[-+*/<>%&^|=!]="
+	 "|--|\\+\\+|<<=?|>>>?=?|&&|\\|\\|"),
+PATTERNS("ruby", "^[ \t]*((class|module|def)[ \t].*)$",
+	 /* -- */
+	 "(@|@@|\\$)?[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.e]+|0[xXbB]?[0-9a-fA-F]+|\\?(\\\\C-)?(\\\\M-)?."
+	 "|//=?|[-+*/<>%&^|=!]=|<<=?|>>=?|===|\\.{1,3}|::|[!=]~"),
 };
 
+#undef IPATTERN
+#undef PATTERNS
+#undef WORD_DEFAULT
+
 struct git_diff_driver_registry {
 	git_strmap *drivers;
 };
@@ -208,14 +236,14 @@ static int git_diff_driver_builtin(
 	}
 
 	git_strmap_insert(reg->drivers, drv->name, drv, error);
+	if (error > 0)
+		error = 0;
 
 done:
-	if (error || !drv) {
+	if (error && drv)
 		git_diff_driver_free(drv);
-		*out = &global_drivers[DIFF_DRIVER_AUTO];
-	} else {
+	else
 		*out = drv;
-	}
 
 	return error;
 }
@@ -324,6 +352,7 @@ static int git_diff_driver_load(
 	git_strmap_insert(reg->drivers, drv->name, drv, error);
 	if (error < 0)
 		goto done;
+	error = 0;
 
 	*out = drv;
 
@@ -349,14 +378,13 @@ int git_diff_driver_lookup(
 	const char *value;
 
 	assert(out);
+	*out = NULL;
 
 	if (!repo || !path || !strlen(path))
-		goto use_auto;
-
-	if ((error = git_attr_get(&value, repo, 0, path, "diff")) < 0)
-		return error;
-
-	if (GIT_ATTR_UNSPECIFIED(value))
+		/* just use the auto value */;
+	else if ((error = git_attr_get(&value, repo, 0, path, "diff")) < 0)
+		/* return error below */;
+	else if (GIT_ATTR_UNSPECIFIED(value))
 		/* just use the auto value */;
 	else if (GIT_ATTR_FALSE(value))
 		*out = &global_drivers[DIFF_DRIVER_BINARY];
@@ -365,17 +393,16 @@ int git_diff_driver_lookup(
 
 	/* otherwise look for driver information in config and build driver */
 	else if ((error = git_diff_driver_load(out, repo, value)) < 0) {
-		if (error != GIT_ENOTFOUND)
-			return error;
-		else
+		if (error == GIT_ENOTFOUND) {
+			error = 0;
 			giterr_clear();
+		}
 	}
 
-use_auto:
 	if (!*out)
 		*out = &global_drivers[DIFF_DRIVER_AUTO];
 
-	return 0;
+	return error;
 }
 
 void git_diff_driver_free(git_diff_driver *driver)
diff --git a/tests/diff/drivers.c b/tests/diff/drivers.c
index c80fad4..4524cd0 100644
--- a/tests/diff/drivers.c
+++ b/tests/diff/drivers.c
@@ -15,6 +15,15 @@ void test_diff_drivers__cleanup(void)
 	g_repo = NULL;
 }
 
+static void overwrite_chmod_at_offset(git_buf *buf, size_t offset)
+{
+	if (cl_is_chmod_supported())
+		return;
+
+	if (buf->size > offset + 6 && memcmp(&buf->ptr[offset], "100644", 6) != 0)
+		memcpy(&buf->ptr[offset], "100644", 6);
+}
+
 void test_diff_drivers__patterns(void)
 {
 	git_config *cfg;
@@ -22,7 +31,7 @@ void test_diff_drivers__patterns(void)
 	git_tree *one;
 	git_diff *diff;
 	git_patch *patch;
-	git_buf buf = GIT_BUF_INIT;
+	git_buf actual = GIT_BUF_INIT;
 	const char *expected0 = "diff --git a/untimely.txt b/untimely.txt\nindex 9a69d96..57fd0cf 100644\n--- a/untimely.txt\n+++ b/untimely.txt\n@@ -22,3 +22,5 @@ Comes through the blood of the vanguards who\n   dreamed--too soon--it had sounded.\r\n \r\n                 -- Rudyard Kipling\r\n+\r\n+Some new stuff\r\n";
 	const char *expected1 = "diff --git a/untimely.txt b/untimely.txt\nindex 9a69d96..57fd0cf 100644\nBinary files a/untimely.txt and b/untimely.txt differ\n";
 	const char *expected2 = "diff --git a/untimely.txt b/untimely.txt\nindex 9a69d96..57fd0cf 100644\n--- a/untimely.txt\n+++ b/untimely.txt\n@@ -22,3 +22,5 @@ Heaven delivers on earth the Hour that cannot be\n   dreamed--too soon--it had sounded.\r\n \r\n                 -- Rudyard Kipling\r\n+\r\n+Some new stuff\r\n";
@@ -45,10 +54,10 @@ void test_diff_drivers__patterns(void)
 	cl_assert_equal_i(1, (int)git_diff_num_deltas(diff));
 
 	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
-	cl_git_pass(git_patch_to_buf(&buf, patch));
-	cl_assert_equal_s(expected0, buf.ptr);
+	cl_git_pass(git_patch_to_buf(&actual, patch));
+	cl_assert_equal_s(expected0, actual.ptr);
 
-	git_buf_free(&buf);
+	git_buf_free(&actual);
 	git_patch_free(patch);
 	git_diff_free(diff);
 
@@ -60,10 +69,10 @@ void test_diff_drivers__patterns(void)
 	cl_assert_equal_i(1, (int)git_diff_num_deltas(diff));
 
 	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
-	cl_git_pass(git_patch_to_buf(&buf, patch));
-	cl_assert_equal_s(expected1, buf.ptr);
+	cl_git_pass(git_patch_to_buf(&actual, patch));
+	cl_assert_equal_s(expected1, actual.ptr);
 
-	git_buf_free(&buf);
+	git_buf_free(&actual);
 	git_patch_free(patch);
 	git_diff_free(diff);
 
@@ -75,10 +84,10 @@ void test_diff_drivers__patterns(void)
 	cl_assert_equal_i(1, (int)git_diff_num_deltas(diff));
 
 	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
-	cl_git_pass(git_patch_to_buf(&buf, patch));
-	cl_assert_equal_s(expected0, buf.ptr);
+	cl_git_pass(git_patch_to_buf(&actual, patch));
+	cl_assert_equal_s(expected0, actual.ptr);
 
-	git_buf_free(&buf);
+	git_buf_free(&actual);
 	git_patch_free(patch);
 	git_diff_free(diff);
 
@@ -92,10 +101,10 @@ void test_diff_drivers__patterns(void)
 	cl_assert_equal_i(1, (int)git_diff_num_deltas(diff));
 
 	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
-	cl_git_pass(git_patch_to_buf(&buf, patch));
-	cl_assert_equal_s(expected1, buf.ptr);
+	cl_git_pass(git_patch_to_buf(&actual, patch));
+	cl_assert_equal_s(expected1, actual.ptr);
 
-	git_buf_free(&buf);
+	git_buf_free(&actual);
 	git_patch_free(patch);
 	git_diff_free(diff);
 
@@ -113,10 +122,10 @@ void test_diff_drivers__patterns(void)
 	cl_assert_equal_i(1, (int)git_diff_num_deltas(diff));
 
 	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
-	cl_git_pass(git_patch_to_buf(&buf, patch));
-	cl_assert_equal_s(expected2, buf.ptr);
+	cl_git_pass(git_patch_to_buf(&actual, patch));
+	cl_assert_equal_s(expected2, actual.ptr);
 
-	git_buf_free(&buf);
+	git_buf_free(&actual);
 	git_patch_free(patch);
 	git_diff_free(diff);
 
@@ -129,7 +138,7 @@ void test_diff_drivers__long_lines(void)
 	git_index *idx;
 	git_diff *diff;
 	git_patch *patch;
-	git_buf buf = GIT_BUF_INIT;
+	git_buf actual = GIT_BUF_INIT;
 	const char *expected = "diff --git a/longlines.txt b/longlines.txt\nindex c1ce6ef..0134431 100644\n--- a/longlines.txt\n+++ b/longlines.txt\n@@ -3,3 +3,5 @@ Phasellus eget erat odio. Praesent at est iaculis, ultricies augue vel, dignissi\n Nam eget dolor fermentum, aliquet nisl at, convallis tellus. Pellentesque rhoncus erat enim, id porttitor elit euismod quis.\n Mauris sollicitudin magna odio, non egestas libero vehicula ut. Etiam et quam velit. Fusce eget libero rhoncus, ultricies felis sit amet, egestas purus.\n Aliquam in semper tellus. Pellentesque adipiscing rutrum velit, quis malesuada lacus consequat eget.\n+newline\n+newline\n";
 
 	g_repo = cl_git_sandbox_init("empty_standard_repo");
@@ -145,18 +154,84 @@ void test_diff_drivers__long_lines(void)
 	cl_git_pass(git_diff_index_to_workdir(&diff, g_repo, NULL, NULL));
 	cl_assert_equal_sz(1, git_diff_num_deltas(diff));
 	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
-	cl_git_pass(git_patch_to_buf(&buf, patch));
+	cl_git_pass(git_patch_to_buf(&actual, patch));
 
 	/* if chmod not supported, overwrite mode bits since anything is possible */
-	if (!cl_is_chmod_supported()) {
-		if (buf.size > 72 && memcmp(&buf.ptr[66], "100644", 6) != 0)
-			memcpy(&buf.ptr[66], "100644", 6);
-	}
+	overwrite_chmod_at_offset(&actual, 66);
 
-	cl_assert_equal_s(expected, buf.ptr);
+	cl_assert_equal_s(expected, actual.ptr);
 
-	git_buf_free(&buf);
+	git_buf_free(&actual);
 	git_patch_free(patch);
 	git_diff_free(diff);
 }
 
+void test_diff_drivers__builtins(void)
+{
+	git_index *idx;
+	git_diff *diff;
+	git_patch *patch;
+	git_buf actual = GIT_BUF_INIT;
+	git_diff_options opts = GIT_DIFF_OPTIONS_INIT;
+	const char *base =
+		"<html>\n<body>\n"
+		"  <h1 id=\"first section\">\n  <ol>\n    <li>item 1.1</li>\n    <li>item 1.2</li>\n    <li>item 1.3</li>\n    <li>item 1.4</li>\n    <li>item 1.5</li>\n    <li>item 1.6</li>\n    <li>item 1.7</li>\n    <li>item 1.8</li>\n    <li>item 1.9</li>\n  </ol>\n  </h1>\n"
+		"  <h1 id=\"second section\">\n  <ol>\n    <li>item 2.1</li>\n    <li>item 2.2</li>\n    <li>item 2.3</li>\n    <li>item 2.4</li>\n    <li>item 2.5</li>\n    <li>item 2.6</li>\n    <li>item 2.7</li>\n    <li>item 2.8</li>\n  </ol>\n  </h1>\n"
+		"  <h1 id=\"third section\">\n  <ol>\n    <li>item 3.1</li>\n    <li>item 3.2</li>\n    <li>item 3.3</li>\n    <li>item 3.4</li>\n    <li>item 3.5</li>\n    <li>item 3.6</li>\n    <li>item 3.7</li>\n    <li>item 3.8</li>\n  </ol>\n  </h1>\n"
+		"</body></html>\n";
+	const char *modified =
+		"<html>\n<body>\n"
+		"  <h1 id=\"first section\">\n  <ol>\n    <li>item 1.1</li>\n    <li>item 1.2 changed</li>\n    <li>item 1.3 changed</li>\n    <li>item 1.4</li>\n    <li>item 1.5</li>\n    <li>item 1.6</li>\n    <li>item 1.7</li>\n    <li>item 1.8</li>\n    <li>item 1.9</li>\n  <li>item 1.10 added</li>\n  </ol>\n  </h1>\n"
+		"  <h1 id=\"second section\">\n  <ol>\n    <li>item 2.1</li>\n    <li>item 2.2</li>\n    <li>item 2.3</li>\n    <li>item 2.4</li>\n    <li>item 2.5</li>\n    <li>item 2.6</li>\n    <li>item 2.7 changed</li>\n    <li>item 2.7.1 added</li>\n    <li>item 2.8</li>\n  </ol>\n  </h1>\n"
+		"  <h1 id=\"third section\">\n  <ol>\n    <li>item 3.1</li>\n    <li>item 3.2</li>\n    <li>item 3.3</li>\n    <li>item 3.4</li>\n    <li>item 3.5</li>\n    <li>item 3.6</li>\n  </ol>\n  </h1>\n"
+		"</body></html>\n";
+	const char *expected_nodriver =
+		"diff --git a/file.html b/file.html\nindex 97b34db..c7dbed3 100644\n--- a/file.html\n+++ b/file.html\n@@ -5,4 +5,4 @@\n     <li>item 1.1</li>\n-    <li>item 1.2</li>\n-    <li>item 1.3</li>\n+    <li>item 1.2 changed</li>\n+    <li>item 1.3 changed</li>\n     <li>item 1.4</li>\n@@ -13,2 +13,3 @@\n     <li>item 1.9</li>\n+  <li>item 1.10 added</li>\n   </ol>\n@@ -23,3 +24,4 @@\n     <li>item 2.6</li>\n-    <li>item 2.7</li>\n+    <li>item 2.7 changed</li>\n+    <li>item 2.7.1 added</li>\n     <li>item 2.8</li>\n@@ -35,4 +37,2 @@\n     <li>item 3.6</li>\n-    <li>item 3.7</li>\n-    <li>item 3.8</li>\n   </ol>\n";
+	const char *expected_driver =
+		"diff --git a/file.html b/file.html\nindex 97b34db..c7dbed3 100644\n--- a/file.html\n+++ b/file.html\n@@ -5,4 +5,4 @@   <h1 id=\"first section\">\n     <li>item 1.1</li>\n-    <li>item 1.2</li>\n-    <li>item 1.3</li>\n+    <li>item 1.2 changed</li>\n+    <li>item 1.3 changed</li>\n     <li>item 1.4</li>\n@@ -13,2 +13,3 @@   <h1 id=\"first section\">\n     <li>item 1.9</li>\n+  <li>item 1.10 added</li>\n   </ol>\n@@ -23,3 +24,4 @@   <h1 id=\"second section\">\n     <li>item 2.6</li>\n-    <li>item 2.7</li>\n+    <li>item 2.7 changed</li>\n+    <li>item 2.7.1 added</li>\n     <li>item 2.8</li>\n@@ -35,4 +37,2 @@   <h1 id=\"third section\">\n     <li>item 3.6</li>\n-    <li>item 3.7</li>\n-    <li>item 3.8</li>\n   </ol>\n";
+
+	g_repo = cl_git_sandbox_init("empty_standard_repo");
+
+	cl_git_mkfile("empty_standard_repo/file.html", base);
+	cl_git_pass(git_repository_index(&idx, g_repo));
+	cl_git_pass(git_index_add_bypath(idx, "file.html"));
+	cl_git_pass(git_index_write(idx));
+	git_index_free(idx);
+
+	cl_git_rewritefile("empty_standard_repo/file.html", modified);
+
+	/* do diff with no special driver */
+
+	opts.interhunk_lines = 1;
+	opts.context_lines = 1;
+
+	cl_git_pass(git_diff_index_to_workdir(&diff, g_repo, NULL, &opts));
+	cl_assert_equal_sz(1, git_diff_num_deltas(diff));
+	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
+	cl_git_pass(git_patch_to_buf(&actual, patch));
+
+	overwrite_chmod_at_offset(&actual, 59);
+
+	cl_assert_equal_s(expected_nodriver, actual.ptr);
+
+	git_buf_free(&actual);
+	git_patch_free(patch);
+	git_diff_free(diff);
+
+	/* do diff with HTML driver */
+
+	cl_git_mkfile("empty_standard_repo/.gitattributes", "*.html diff=html\n");
+
+	cl_git_pass(git_diff_index_to_workdir(&diff, g_repo, NULL, &opts));
+	cl_assert_equal_sz(1, git_diff_num_deltas(diff));
+	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
+	cl_git_pass(git_patch_to_buf(&actual, patch));
+
+	overwrite_chmod_at_offset(&actual, 59);
+
+	cl_assert_equal_s(expected_driver, actual.ptr);
+
+	git_buf_free(&actual);
+	git_patch_free(patch);
+	git_diff_free(diff);
+}