Re: [PATCH 1/1] Makefile: use `git ls-files` to list header files, if possible

[Junio C Hamano <gitster@pobox.com>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

>> After a normal build, with dynamic dependency checking on, we would
>> have sufficient information to figure it out.  Would that help?
>
> Yes, *if* the dynamic dependency checking is in effect (read: if we are
> compiling with GCC).
>
> However, I think that one of the benefits of the current approach is that
> hdr-check finds issues also in headers that are *not* part of the current
> build. Read: once hdr-check is run as part of the CI build, it is harder
> for some random contributor to break hdr-check for somebody else with
> different compile time options.

Sure.  That is exactly why we have multiple configurations at the
CI, hopefully more than each individual contributor has at hand so
that CI can give more coverage than any single individual can test.

What I was assuming was that at least one of these multiple
configurations would cover the case where sha256/gcrypt.h truly is
used, because that particular build is configured to use the system
header and library.  And it would be a far better approach to make
that build check also for the header, if we can cover all the
problematic (in the same sense as the sha256/gcrypt.h) header files,
than unconditionally "checking" without knowing the prerequisite and
causing a false positive.

Having said that, the optional use of ls-files introduced by the
patch in question is a valid incremental improvement over the
current Makefile, so it is a pretty much independent/orthogonal
issue.