Re: [PATCH 3/6] Makefile: refactor out "ln || ln -s || cp" pattern

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 29, 2021, 22:24 UTC
Message-ID: <xmqqsg4dha3i.fsf@gitster.g>
In-Reply-To: <patch-3.7-bde9de756b4-20210329T162327Z-avarab@gmail.com>

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

Show 27 quoted lines

> Refactor out the hard-to-read and maintain "ln || ln -s || cp"
> pattern.
>
> This was initially added in 3e073dc5611 (Makefile: always provide a
> fallback when hardlinks fail, 2008-08-25), but since then it's become
> a lot more complex as we've added:
>
>  * 3426e34fedd (Add NO_CROSS_DIRECTORY_HARDLINKS support to the
>    Makefile, 2009-05-11)
>
>  * NO_INSTALL_HARDLINKS in 70de5e65e8c (Makefile:
>    NO_INSTALL_HARDLINKS, 2012-05-02)
>
>  * INSTALL_SYMLINKS in ad874608d8c (Makefile: optionally symlink
>    libexec/git-core binaries to bin/git, 2018-03-13)
>
>  * SKIP_DASHED_BUILT_INS 179227d6e21 (Optionally skip linking/copying
>    the built-ins, 2020-09-21)
>
> Each of those commits had to add a new special-case to this code,
> resulting in quite an unmaintainable mess for adding any sort of new
> option.
>
> Let's use the newly introduced ln-or-cp.sh script instead, note that
> we only sometimes pass the --no-cross-directory-hardlinks option, per
> the previous behavior. The target of the "ln -s" is also another
> special snowflake, but we're careful to carry that forward.

Nice. These explicit command-line options to the helper may be harder to initially write and maintain than just exporting the relevant $(MAKE) macros and using it from the helper, but once it works correctly, it is much easier to see what is going on.

And obviously, if we want to fix the "I do not ever want to see any symlinks", it is very clear that main_with_fallbacks is where the change needs to go.

Raelly nice.