Implement patience and minimal diff flags

It seems that to implement these options, we just have to pass
the appropriate flags through to the libxdiff code taken from
core git.  So let's do it (and add a test).

include/git2/diff.h

@@ -175,8 +175,11 @@ typedef enum {
 	 */
 	GIT_DIFF_SHOW_UNMODIFIED = (1u << 26),
 
-	/** Use the "patience diff" algorithm (currently unimplemented) */
+	/** Use the "patience diff" algorithm */
 	GIT_DIFF_PATIENCE = (1u << 28),
+	/** Take extra time to find minimal diff */
+	GIT_DIFF_MINIMAL = (1 << 29),
+
 } git_diff_option_t;
 
 /**

src/diff_xdiff.c

@@ -222,6 +222,11 @@ void git_xdiff_init(git_xdiff_output *xo, const git_diff_options *opts)
 	if (flags & GIT_DIFF_IGNORE_WHITESPACE_EOL)
 		xo->params.flags |= XDF_IGNORE_WHITESPACE_AT_EOL;
 
+	if (flags & GIT_DIFF_PATIENCE)
+		xo->params.flags |= XDF_PATIENCE_DIFF;
+	if (flags & GIT_DIFF_MINIMAL)
+		xo->params.flags |= XDF_NEED_MINIMAL;
+
 	memset(&xo->callback, 0, sizeof(xo->callback));
 	xo->callback.outf = git_xdiff_cb;
 }

tests-clar/diff/workdir.c

@@ -1282,3 +1282,50 @@ void test_diff_workdir__untracked_with_bom(void)
 
 	git_diff_free(diff);
 }
+
+void test_diff_workdir__patience_diff(void)
+{
+	git_index *index;
+	git_diff_options opts = GIT_DIFF_OPTIONS_INIT;
+	git_diff *diff = NULL;
+	git_patch *patch = NULL;
+	char *as_str = NULL;
+	const char *expected_normal = "diff --git a/test.txt b/test.txt\nindex 34a5acc..d52725f 100644\n--- a/test.txt\n+++ b/test.txt\n@@ -1,10 +1,7 @@\n When I wrote this\n I did not know\n-how to create\n-a patience diff\n I did not know\n how to create\n+a patience diff\n another problem\n-I did not know\n-how to create\n a minimal diff\n";
+	const char *expected_patience = "diff --git a/test.txt b/test.txt\nindex 34a5acc..d52725f 100644\n--- a/test.txt\n+++ b/test.txt\n@@ -1,10 +1,7 @@\n When I wrote this\n I did not know\n+I did not know\n how to create\n a patience diff\n-I did not know\n-how to create\n another problem\n-I did not know\n-how to create\n a minimal diff\n";
+
+	g_repo = cl_git_sandbox_init("empty_standard_repo");
+	cl_repo_set_bool(g_repo, "core.autocrlf", true);
+	cl_git_pass(git_repository_index(&index, g_repo));
+
+	cl_git_mkfile(
+		"empty_standard_repo/test.txt",
+		"When I wrote this\nI did not know\nhow to create\na patience diff\nI did not know\nhow to create\nanother problem\nI did not know\nhow to create\na minimal diff\n");
+	cl_git_pass(git_index_add_bypath(index, "test.txt"));
+	cl_repo_commit_from_index(NULL, g_repo, NULL, 1372350000, "Base");
+
+	cl_git_rewritefile(
+		"empty_standard_repo/test.txt",
+		"When I wrote this\nI did not know\nI did not know\nhow to create\na patience diff\nanother problem\na minimal diff\n");
+
+	cl_git_pass(git_diff_index_to_workdir(&diff, g_repo, NULL, &opts));
+	cl_assert_equal_i(1, git_diff_num_deltas(diff));
+	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
+	cl_git_pass(git_patch_to_str(&as_str, patch));
+
+	cl_assert_equal_s(expected_normal, as_str);
+	git__free(as_str);
+	git_patch_free(patch);
+	git_diff_free(diff);
+
+	opts.flags |= GIT_DIFF_PATIENCE;
+
+	cl_git_pass(git_diff_index_to_workdir(&diff, g_repo, NULL, &opts));
+	cl_assert_equal_i(1, git_diff_num_deltas(diff));
+	cl_git_pass(git_patch_from_diff(&patch, diff, 0));
+	cl_git_pass(git_patch_to_str(&as_str, patch));
+
+	cl_assert_equal_s(expected_patience, as_str);
+	git__free(as_str);
+	git_patch_free(patch);
+	git_diff_free(diff);
+}