Merge branch 'jc/maint-add-sync-stat' into maint

* jc/maint-add-sync-stat:
t2200: test more cases of "add -u"
git-add: make the entry stat-clean after re-adding the same contents
ce_match_stat, run_diff_files: use symbolic constants for readability

diff --cc builtin-add.c
Simple merge

diff --cc cache.h
Simple merge