Re: [Request] Git reset should be able to ignore file permissions

From: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Date: Jun 18, 2013, 14:06 UTC
Message-ID: <vpq7ghrqzrv.fsf@anie.imag.fr>
In-Reply-To: <CACuz9s1KGKsL-pGftAtAWyX5gUA5c-PYyJUSstf+xw151rZLtA@mail.gmail.com>

Alexander Nestorov <alexandernst@gmail.com> writes:

> I'm not trying to ignore the x bit, what I'm trying to do is make
> "git reset" checkout only the files that actually changed instead
> of checking out all the files with different permissions than the
> ones git thinks they should have.

Ah, OK, you want "git reset --hard" to just do a chmod, which would not touch the file's mtime (but only the ctime).

Then, it's even easier to demonstrate: just "touch" instead of chmod. Indeed:

$ touch myfile; sleep 2 $ strace -f git reset --hard 2>&1 | grep myfile lstat("myfile", {st_mode=S_IFREG|0755, st_size=5, ...}) = 0 lstat("myfile", {st_mode=S_IFREG|0755, st_size=5, ...}) = 0 unlink("myfile") = 0 open("myfile", O_WRONLY|O_CREAT|O_EXCL, 0777) = 4

(sleep 2 is needed in the demonstration to avoid the "racy git" safeties, but it's not really important)

Git doesn't even try to read the file content: once it detected that the stat information changed, it rewrite the file without looking at its content. It's faster this way for files that actually changed.

> Said with other word: when you run "git reset", git does a "status"
> and checkouts all the files that showed up from the "status".

No, it's indeed the opposite: "status" re-checks the content of changed files, and update the stat-cache in the index accordingly if the content actually didn't change.

Runing "git status" before "git reset --hard" should solve your problem. The part of "git status" of interest is "git update-index --refresh":

$ touch myfile; sleep 2 $ git update-index --refresh $ strace -f git reset --hard 2>&1 | grep myfile lstat("myfile", {st_mode=S_IFREG|0755, st_size=5, ...}) = 0 $

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/