Re: [PATCH resend] perl/Makefile.PL: teach makefiles about possible old Error.pm files

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

Chris Frey <cdfrey@foursquare.net> writes:

> If a previous version of git was installed on a system without a
> proper Error.pm, git will install its own.  But the next time
> git is compiled on that system, that Error.pm will prevent git from
> installing its own copy the second time.  This causes a broken
> git install on such systems.
>
> This patch fixes this bug by tagging git's Error.pm with an
> INSTALLED_BY flag, and checking for it during the compile.

I think this is a wrong direction to go.

We do not currently deal with broken installations, and "stow" is just one
easy way to install and keep a stale version.  The right solution would be
to check if "Error.pm" we find on the system (be it installed by previous
incarnation of git or some other packages) works as expected, and refrain
from using it if it doesn't.

When the system has a slightly older version of Error.pm, it does not
really matter if that old one case from our own Error.pm (because back
then the system did not have Error.pm at all), or the user installed a
slightly older version of Error.pm from elsewhere.

IOW, I won't be interested in a solution that adds INSTALLED_BY.  Even if
it is ours, as long as it is fresh enough, there is no reason to replace
it with a new copy.  Even if it is _not_ ours, if it is stale and does not
work as we expect, we might have to install our own on our path.