diff: fix the diffing of a concrete blob against a null one

2 files changed, 62 insertions, 35 deletions

diff --git a/src/diff_output.c b/src/diff_output.c
index 788c8b8f0..dbcc89fa5 100644
--- a/src/diff_output.c
+++ b/src/diff_output.c
@@ -686,7 +686,6 @@ int git_diff_print_patch(
 	return error;
 }
 
-
 int git_diff_blobs(
 	git_blob *old_blob,
 	git_blob *new_blob,
@@ -701,44 +700,43 @@ int git_diff_blobs(
 	xpparam_t xdiff_params;
 	xdemitconf_t xdiff_config;
 	xdemitcb_t xdiff_callback;
+	git_blob *new, *old;
+
+	memset(&delta, 0, sizeof(delta));
+
+	new = new_blob;
+	old = old_blob;
 
 	if (options && (options->flags & GIT_DIFF_REVERSE)) {
-		git_blob *swap = old_blob;
-		old_blob = new_blob;
-		new_blob = swap;
+		git_blob *swap = old;
+		old = new;
+		new = swap;
 	}
 
-	if (old_blob) {
-		old_data.ptr  = (char *)git_blob_rawcontent(old_blob);
-		old_data.size = git_blob_rawsize(old_blob);
+	if (old) {
+		old_data.ptr  = (char *)git_blob_rawcontent(old);
+		old_data.size = git_blob_rawsize(old);
+		git_oid_cpy(&delta.old_file.oid, git_object_id((const git_object *)old));
 	} else {
 		old_data.ptr  = "";
 		old_data.size = 0;
 	}
 
-	if (new_blob) {
-		new_data.ptr  = (char *)git_blob_rawcontent(new_blob);
-		new_data.size = git_blob_rawsize(new_blob);
+	if (new) {
+		new_data.ptr  = (char *)git_blob_rawcontent(new);
+		new_data.size = git_blob_rawsize(new);
+		git_oid_cpy(&delta.new_file.oid, git_object_id((const git_object *)new));
 	} else {
 		new_data.ptr  = "";
 		new_data.size = 0;
 	}
 
 	/* populate a "fake" delta record */
-	delta.status = old_data.ptr ?
-		(new_data.ptr ? GIT_DELTA_MODIFIED : GIT_DELTA_DELETED) :
-		(new_data.ptr ? GIT_DELTA_ADDED : GIT_DELTA_UNTRACKED);
-	delta.old_file.mode = 0000000; /* can't know the truth from a blob alone */
-	delta.new_file.mode = 0000000;
-	git_oid_cpy(&delta.old_file.oid, git_object_id((const git_object *)old_blob));
-	git_oid_cpy(&delta.new_file.oid, git_object_id((const git_object *)new_blob));
-	delta.old_file.path = NULL;
-	delta.new_file.path = NULL;
+	delta.status = new ?
+		(old ? GIT_DELTA_MODIFIED : GIT_DELTA_ADDED) :
+		(old ? GIT_DELTA_DELETED : GIT_DELTA_UNTRACKED);
 	delta.old_file.size = old_data.size;
 	delta.new_file.size = new_data.size;
-	delta.old_file.flags = 0;
-	delta.new_file.flags = 0;
-	delta.similarity = 0;
 
 	info.diff    = NULL;
 	info.delta   = δ
diff --git a/tests-clar/diff/blob.c b/tests-clar/diff/blob.c
index 65b350005..9364bdc6d 100644
--- a/tests-clar/diff/blob.c
+++ b/tests-clar/diff/blob.c
@@ -2,23 +2,38 @@
 #include "diff_helpers.h"
 
 static git_repository *g_repo = NULL;
+static diff_expects exp;
+static git_diff_options opts;
+static git_blob *d;
 
 void test_diff_blob__initialize(void)
 {
+	git_oid d_oid;
+
 	g_repo = cl_git_sandbox_init("attr");
+
+	memset(&opts, 0, sizeof(opts));
+	opts.context_lines = 1;
+	opts.interhunk_lines = 1;
+
+	memset(&exp, 0, sizeof(exp));
+
+	/* tests/resources/attr/root_test4.txt */
+	cl_git_pass(git_oid_fromstrn(&d_oid, "fe773770c5a6", 12));
+	cl_git_pass(git_blob_lookup_prefix(&d, g_repo, &d_oid, 6));
 }
 
 void test_diff_blob__cleanup(void)
 {
+	git_blob_free(d);
+
 	cl_git_sandbox_cleanup();
 }
 
 void test_diff_blob__can_compare_text_blobs(void)
 {
-	git_blob *a, *b, *c, *d;
-	git_oid a_oid, b_oid, c_oid, d_oid;
-	git_diff_options opts = {0};
-	diff_expects exp;
+	git_blob *a, *b, *c;
+	git_oid a_oid, b_oid, c_oid;
 
 	/* tests/resources/attr/root_test1 */
 	cl_git_pass(git_oid_fromstrn(&a_oid, "45141a79", 8));
@@ -32,16 +47,8 @@ void test_diff_blob__can_compare_text_blobs(void)
 	cl_git_pass(git_oid_fromstrn(&c_oid, "c96bbb2c2557a832", 16));
 	cl_git_pass(git_blob_lookup_prefix(&c, g_repo, &c_oid, 8));
 
-	/* tests/resources/attr/root_test4.txt */
-	cl_git_pass(git_oid_fromstrn(&d_oid, "fe773770c5a6", 12));
-	cl_git_pass(git_blob_lookup_prefix(&d, g_repo, &d_oid, 6));
-
 	/* Doing the equivalent of a `git diff -U1` on these files */
 
-	opts.context_lines = 1;
-	opts.interhunk_lines = 1;
-
-	memset(&exp, 0, sizeof(exp));
 	cl_git_pass(git_diff_blobs(
 		a, b, &opts, &exp, diff_hunk_fn, diff_line_fn));
 
@@ -86,6 +93,28 @@ void test_diff_blob__can_compare_text_blobs(void)
 	git_blob_free(a);
 	git_blob_free(b);
 	git_blob_free(c);
-	git_blob_free(d);
 }
 
+void test_diff_blob__can_compare_against_null_blobs(void)
+{
+	git_blob *e = NULL;
+
+	cl_git_pass(git_diff_blobs(
+		d, e, &opts, &exp, diff_hunk_fn, diff_line_fn));
+
+	cl_assert(exp.hunks == 1);
+	cl_assert(exp.hunk_old_lines == 14);
+	cl_assert(exp.lines == 14);
+	cl_assert(exp.line_dels == 14);
+
+	opts.flags |= GIT_DIFF_REVERSE;
+	memset(&exp, 0, sizeof(exp));
+
+	cl_git_pass(git_diff_blobs(
+		d, e, &opts, &exp, diff_hunk_fn, diff_line_fn));
+
+	cl_assert(exp.hunks == 1);
+	cl_assert(exp.hunk_new_lines == 14);
+	cl_assert(exp.lines == 14);
+	cl_assert(exp.line_adds == 14);
+}