bug#35542: Installer does not display full backtrace on error

[Danny Milosavljevic <dannym@scratchpost.org>]

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Hi Mathieu,

On Sat, 04 May 2019 18:14:48 +0200
Mathieu Othacehe <m.othacehe@gmail.com> wrote:

> Thanks for testing Florian. Based on Danny suggestion we could set
> COLUMNS to 200 to have a more verbose backtrace (like guix itself).

Good idea in principle.

> Using higher values, the backtrace becomes really long and harder to
> read. WDYT?

When we have a designed error message, we present one--and, there, brevity
is good.

But backtraces are for developers only anyway, and are not designed error
messages.
So for backtraces I'm against throwing *anything* of the backtrace
message away because we don't know what part of it is important (if we
did, we'd print a designed error message instead--I'm all for doing that).

I think this is something the default Guile setting gets wrong and I
don't understand how it can be a good idea to suppress half of a
message intended to simplify debugging for a developer "because it's
too long".  The length is nothing compared to the amount of text a
developer has to type in order to reproduce the missing parts later on,
if it's even possible.

I'm even actually using core files (including attaching to them using a
debugger in order to examine variable values), so I might be an outlier.

So I'd be for either presenting the entire backtrace or suppressing the
entire backtrace, not having teaser backtraces :)

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