Re: [PATCH v6 3/9] packed-backend: check whether the "packed-refs" is regular file

From: Junio C Hamano <gitster@pobox.com>
Date: Feb 25, 2025, 17:44 UTC
Message-ID: <xmqq1pvlly1f.fsf@gitster.g>
In-Reply-To: <Z73D3PdEFk_nciH7@ArchLinux>

shejialuo <shejialuo@gmail.com> writes:

Show 9 quoted lines

> Although "git-fsck(1)" and "packed-backend.c" will check some
> consistency and correctness of "packed-refs" file, they never check the
> filetype of the "packed-refs". Let's verify that the "packed-refs" has
> the expected filetype, confirming it is created by "git pack-refs"
> command.
>
> Use "lstat" to check the file mode. If we cannot check the file status
> due to there is no such file this is OK because there is a possibility
> that there is no "packed-refs" in the repo.

Can this be done _after_ the open_nofollow() check you had in the previous round noticed a problem? Even though we are trying to notice and find problems in the given repository, it is generally a good idea to optimize for the more common case (i.e. the file is a regular one and not a symbolic link or directory or anything funny). Something along the lines of

	fd = open_nofollow(...);
	if (fd < 0) {
		lstat() to inspect the details
	} else if (fstat(fd, &st) < 0) {
		... cannot tell what we opened ...
	} else if (!S_ISREG(st.st_mode)) {
		... we opened something funny ...
	} else {
		... the thing is a regular file as expected ...
	}

perhaps?