Merge branch 'rs/diff-files-r-find-copies-fix' into next

"git diff-files -R --find-copies-harder" has been taught to use
the potential copy sources from the index correctly.

* rs/diff-files-r-find-copies-fix:
  diff-files: fix copy detection

Author: gitster

diff-lib.c

@@ -226,8 +226,12 @@ void run_diff_files(struct rev_info *revs, unsigned int option)
 				continue;
 		}
 
-		if (ce_uptodate(ce) || ce_skip_worktree(ce))
+		if (ce_uptodate(ce) || ce_skip_worktree(ce)) {
+			if (revs->diffopt.flags.find_copies_harder)
+				diff_same(&revs->diffopt, ce->ce_mode,
+					  &ce->oid, ce->name);
 			continue;
+		}
 
 		/*
 		 * When CE_VALID is set (via "update-index --assume-unchanged"
@@ -272,8 +276,10 @@ void run_diff_files(struct rev_info *revs, unsigned int option)
 		if (!changed && !dirty_submodule) {
 			ce_mark_uptodate(ce);
 			mark_fsmonitor_valid(istate, ce);
-			if (!revs->diffopt.flags.find_copies_harder)
-				continue;
+			if (revs->diffopt.flags.find_copies_harder)
+				diff_same(&revs->diffopt, newmode,
+					  &ce->oid, ce->name);
+			continue;
 		}
 		oldmode = ce->ce_mode;
 		old_oid = &ce->oid;

t/t4007-rename-3.sh

@@ -67,7 +67,28 @@ test_expect_success 'copy, limited to a subtree' '
 '
 
 test_expect_success 'tweak work tree' '
-	rm -f path0/COPYING &&
+	rm -f path0/COPYING
+'
+
+cat >expected <<EOF
+:100644 100644 $blob $blob C100	path1/COPYING	path0/COPYING
+EOF
+
+# The cache has path0/COPYING and path1/COPYING, the working tree only
+# path1/COPYING.  This is a deletion -- we don't treat deduplication
+# specially.  In reverse it should be detected as a copy, though.
+test_expect_success 'copy detection, files to index' '
+	git diff-files -C --find-copies-harder -R >current &&
+	compare_diff_raw current expected
+'
+
+test_expect_success 'copy detection, files to preloaded index' '
+	GIT_TEST_PRELOAD_INDEX=1 \
+	git diff-files -C --find-copies-harder -R >current &&
+	compare_diff_raw current expected
+'
+
+test_expect_success 'tweak index' '
 	git update-index --remove path0/COPYING
 '
 # In the tree, there is only path0/COPYING.  In the cache, path0 does