Re: [PATCH v2 22/22] untracked cache: guard and disable on system changes

If the user enables untracked cache, then

 - move worktree to an unsupported filesystem
 - or simply upgrade OS
 - or move the whole (portable) disk from one machine to another
 - or access a shared fs from another machine

there's no guarantee that untracked cache can still function properly.
Record the worktree location and OS footprint in the cache. If it
changes, err on the safe side and disable the cache. The user can
'update-index --untracked-cache' again to make sure all conditions are
met.

This change does not cover all bases, you can fool it if you try
hard. The point is to stop accidents.

Signed-off-by: Nguyễn Thái Ngọc Duy <redacted>
---

diff --git a/test-dump-untracked-cache.c b/test-dump-untracked-cache.c
index 710441e..25d855d 100644
--- a/test-dump-untracked-cache.c
+++ b/test-dump-untracked-cache.c

@@ -44,6 +44,7 @@ int main(int ac, char **av)
 {
        struct untracked_cache *uc;
        struct strbuf base = STRBUF_INIT;
+       setup_git_directory();