Merge branch 'ar/diff-args-osx-precompose'

Many commands normalize command line arguments from NFD to NFC
variant of UTF-8 on OSX, but commands in the "diff" family did
not, causing "git diff $path" to complain that no such path is
known to Git.  They have been taught to do the normalization.

* ar/diff-args-osx-precompose:
  diff: run arguments through precompose_argv

builtin/diff-tree.c

@@ -114,6 +114,8 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 	opt->disable_stdin = 1;
 	memset(&s_r_opt, 0, sizeof(s_r_opt));
 	s_r_opt.tweak = diff_tree_tweak_rev;
+
+	precompose_argv(argc, argv);
 	argc = setup_revisions(argc, argv, opt, &s_r_opt);
 
 	while (--argc > 0) {