Re: [PATCH 6/6] Makefile: add a INSTALL_FALLBACK_LN_CP mode

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 29, 2021, 22:53 UTC
Message-ID: <xmqqeefxh8rl.fsf@gitster.g>
In-Reply-To: <patch-6.7-9ada8979890-20210329T162327Z-avarab@gmail.com>

Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:

Show 9 quoted lines

> Change the default behavior on "make install" where we fallback
> through a chain of "ln || ln -s || cp" to instead error out when we
> can't symlink or hardlink, and not then fallback on a "cp" (or from a
> symlink to hardlink etc.).
>
> The fallback behavior was introduced in 3e073dc5611 (Makefile: always
> provide a fallback when hardlinks fail, 2008-08-25), since then we've
> gained the ability to specify e.g. that we'd like symlinks via the
> INSTALL_SYMLINKS setting.

Hmph, I am not so sure. "Use hardlink if we can, as that would not consume inode, but where hardlinks cannot be used, it is OK to use symlink, and I do not want to waste disk blocks with cp" is probably one of the sensible wishes, but at least without "ln || ln -s" fallback, you cannot do that, no?

So I would understand if there are two orthogonal knobs

 - the order of preference (e.g. hardlink > symlink > copy)
 - which ones are allowed (e.g. "no symlinks please")

but I cannot quite imagine how a system without any fallback would be useful.

> +main_no_fallbacks () {
> +	if test -n "$no_install_hardlinks" -a -z "$install_symlinks"

As the values of these variables are (presumably) tightly under our control, the use of -a/-o with test may be safe in these examples, but to avoid letting clueless shell script newbies to cargo cult this code, let's use the safer "test -n A && test -z B" form.