Make core.safecrlf work on LF-ending platforms

If you enabled core.safecrlf on an LF-ending platform, we would
error even for files with all LFs.  We should only be warning on
irreversible mappings, I think.

src/crlf.c

@@ -139,7 +139,9 @@ static int crlf_apply_to_odb(
 			return GIT_PASSTHROUGH;
 
 		/* If safecrlf is enabled, sanity-check the result. */
-		if (stats.cr != stats.crlf || stats.lf != stats.crlf) {
+		if (stats.cr != stats.crlf ||
+			(stats.crlf > 0 && stats.lf != stats.crlf)) {
+
 			switch (ca->safe_crlf) {
 			case GIT_SAFE_CRLF_FAIL:
 				giterr_set(

tests/filter/crlf.c

@@ -103,12 +103,12 @@ void test_filter_crlf__with_safecrlf(void)
 	cl_git_fail(git_filter_list_apply_to_data(&out, fl, &in));
 	cl_assert_equal_i(giterr_last()->klass, GITERR_FILTER);
 
-	/* Normalized \n fails with safecrlf */
+	/* Normalized \n is reversible, so does not fail with safecrlf */
 	in.ptr = "Normal\nLF\nonly\nline-endings.\n";
 	in.size = strlen(in.ptr);
 
-	cl_git_fail(git_filter_list_apply_to_data(&out, fl, &in));
-	cl_assert_equal_i(giterr_last()->klass, GITERR_FILTER);
+	cl_git_pass(git_filter_list_apply_to_data(&out, fl, &in));
+	cl_assert_equal_s(in.ptr, out.ptr);
 
 	git_filter_list_free(fl);
 	git_buf_free(&out);

tests/index/crlf.c

@@ -134,3 +134,21 @@ void test_index_crlf__autocrlf_input_text_auto_attr(void)
 	cl_git_pass(git_oid_fromstr(&oid, FILE_OID_LF));
 	cl_assert(git_oid_cmp(&oid, &entry->id) == 0);
 }
+
+void test_index_crlf__safecrlf_true_no_attrs(void)
+{
+	cl_repo_set_bool(g_repo, "core.autocrlf", true);
+	cl_repo_set_bool(g_repo, "core.safecrlf", true);
+
+	cl_git_mkfile("crlf/newfile.txt", ALL_LF_TEXT_RAW);
+	cl_git_pass(git_index_add_bypath(g_index, "newfile.txt"));
+
+	cl_git_mkfile("crlf/newfile.txt", ALL_CRLF_TEXT_RAW);
+	cl_git_pass(git_index_add_bypath(g_index, "newfile.txt"));
+
+	cl_git_mkfile("crlf/newfile.txt", MORE_CRLF_TEXT_RAW);
+	cl_git_fail(git_index_add_bypath(g_index, "newfile.txt"));
+
+	cl_git_mkfile("crlf/newfile.txt", MORE_LF_TEXT_RAW);
+	cl_git_fail(git_index_add_bypath(g_index, "newfile.txt"));
+}