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

diff --cc builtin/diff-tree.c
Simple merge

diff --cc builtin/diff.c
index 343c6b8f2522a295a6148434572e77a3a3c5a16b,5b8039cbc7d51a52f0a9bd3e7cc84e722e606555..b7a9405d9fbec46edf99637557d7499fb58c4d77
--- 1/builtin/diff.c
--- 2/builtin/diff.c
+++ b/builtin/diff.c
@@@ -318,8 -318,8 +318,9 @@@ int cmd_diff(int argc, const char **arg
  
        if (!no_index)
                gitmodules_config();
 +      init_diff_ui_defaults();
        git_config(git_diff_ui_config, NULL);
+       precompose_argv(argc, argv);
  
        init_revisions(&rev, prefix);