Fix --assume-unchanged support

This was never really working right because we were checking the
wrong flag and not checking it in all the places that we need to
be checking it.  I finally got around to writing a test and adding
actual support for it.

src/diff.c

@@ -63,13 +63,16 @@ static int diff_notify(
 
 static int diff_delta__from_one(
 	git_diff *diff,
-	git_delta_t   status,
+	git_delta_t status,
 	const git_index_entry *entry)
 {
 	git_diff_delta *delta;
 	const char *matched_pathspec;
 	int notify_res;
 
+	if ((entry->flags & GIT_IDXENTRY_VALID) != 0)
+		return 0;
+
 	if (status == GIT_DELTA_IGNORED &&
 		DIFF_FLAG_ISNT_SET(diff, GIT_DIFF_INCLUDE_IGNORED))
 		return 0;
@@ -426,7 +429,7 @@ static int diff_list_apply_options(
 		diff->diffcaps = diff->diffcaps | GIT_DIFFCAPS_HAS_SYMLINKS;
 
 	if (!git_repository__cvar(&val, repo, GIT_CVAR_IGNORESTAT) && val)
-		diff->diffcaps = diff->diffcaps | GIT_DIFFCAPS_ASSUME_UNCHANGED;
+		diff->diffcaps = diff->diffcaps | GIT_DIFFCAPS_IGNORE_STAT;
 
 	if ((diff->opts.flags & GIT_DIFF_IGNORE_FILEMODE) == 0 &&
 		!git_repository__cvar(&val, repo, GIT_CVAR_FILEMODE) && val)
@@ -701,9 +704,8 @@ static int maybe_modified(
 		nmode = (nmode & ~MODE_BITS_MASK) | (omode & MODE_BITS_MASK);
 
 	/* support "assume unchanged" (poorly, b/c we still stat everything) */
-	if ((diff->diffcaps & GIT_DIFFCAPS_ASSUME_UNCHANGED) != 0)
-		status = (oitem->flags_extended & GIT_IDXENTRY_INTENT_TO_ADD) ?
-			GIT_DELTA_MODIFIED : GIT_DELTA_UNMODIFIED;
+	if ((oitem->flags & GIT_IDXENTRY_VALID) != 0)
+		status = GIT_DELTA_UNMODIFIED;
 
 	/* support "skip worktree" index bit */
 	else if ((oitem->flags_extended & GIT_IDXENTRY_SKIP_WORKTREE) != 0)

src/diff.h

@@ -23,7 +23,7 @@
 
 enum {
 	GIT_DIFFCAPS_HAS_SYMLINKS     = (1 << 0), /* symlinks on platform? */
-	GIT_DIFFCAPS_ASSUME_UNCHANGED = (1 << 1), /* use stat? */
+	GIT_DIFFCAPS_IGNORE_STAT      = (1 << 1), /* use stat? */
 	GIT_DIFFCAPS_TRUST_MODE_BITS  = (1 << 2), /* use st_mode? */
 	GIT_DIFFCAPS_TRUST_CTIME      = (1 << 3), /* use st_ctime? */
 	GIT_DIFFCAPS_USE_DEV          = (1 << 4), /* use st_dev? */

tests-clar/diff/workdir.c

@@ -63,6 +63,60 @@ void test_diff_workdir__to_index(void)
 	git_diff_free(diff);
 }
 
+void test_diff_workdir__to_index_with_assume_unchanged(void)
+{
+	git_diff_options opts = GIT_DIFF_OPTIONS_INIT;
+	git_diff *diff = NULL;
+	git_index *idx = NULL;
+	diff_expects exp;
+	const git_index_entry *iep;
+	git_index_entry ie;
+
+	g_repo = cl_git_sandbox_init("status");
+
+	/* do initial diff */
+
+	cl_git_pass(git_diff_index_to_workdir(&diff, g_repo, NULL, &opts));
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(8, exp.files);
+	cl_assert_equal_i(0, exp.file_status[GIT_DELTA_ADDED]);
+	cl_assert_equal_i(4, exp.file_status[GIT_DELTA_DELETED]);
+	cl_assert_equal_i(4, exp.file_status[GIT_DELTA_MODIFIED]);
+	git_diff_free(diff);
+
+	/* mark a couple of entries with ASSUME_UNCHANGED */
+
+	cl_git_pass(git_repository_index(&idx, g_repo));
+
+	cl_assert((iep = git_index_get_bypath(idx, "modified_file", 0)) != NULL);
+	memcpy(&ie, iep, sizeof(ie));
+	ie.flags |= GIT_IDXENTRY_VALID;
+	cl_git_pass(git_index_add(idx, &ie));
+
+	cl_assert((iep = git_index_get_bypath(idx, "file_deleted", 0)) != NULL);
+	memcpy(&ie, iep, sizeof(ie));
+	ie.flags |= GIT_IDXENTRY_VALID;
+	cl_git_pass(git_index_add(idx, &ie));
+
+	cl_git_pass(git_index_write(idx));
+	git_index_free(idx);
+
+	/* redo diff and see that entries are skipped */
+
+	cl_git_pass(git_diff_index_to_workdir(&diff, g_repo, NULL, &opts));
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(6, exp.files);
+	cl_assert_equal_i(0, exp.file_status[GIT_DELTA_ADDED]);
+	cl_assert_equal_i(3, exp.file_status[GIT_DELTA_DELETED]);
+	cl_assert_equal_i(3, exp.file_status[GIT_DELTA_MODIFIED]);
+	git_diff_free(diff);
+
+}
+
 void test_diff_workdir__to_tree(void)
 {
 	/* grabbed a couple of commit oids from the history of the attr repo */