Bug#1091324: devscripts: New --reverse mode for debbisect

[Santiago Vila]

Package: devscripts
Version: 2.24.8
Severity: wishlist
Tags: patch

Hi. A few weeks ago I asked here how a bisect should be done
when bad < good and the aim is to know when something was fixed:

https://lists.debian.org/debian-mentors/2024/11/msg00056.html

The simple solution is to use another script with the exit status reversed.

However, when doing that, we have to change the way we call things.
Good becomes bad and bad becomes good, and if we cut and paste the
final output from debbisect, we have to clarify that the meanings
are swapped.

A better solution is to implement this "natively" in debbisect,
which is what the attached patch tries to do.

It mostly works for me, but it probably needs more testing.

I've also opened a Merge Request in salsa in case it helps.

Thanks.

[Santiago Vila]

Hi josch.

Today I made a debbisect using my modified script and this happened:

bisection finished successfully
last bad timestamp: 20241028T023949Z
first good timestamp: 20241028T090451Z
ERROR:root:no difference -- this should never happen


I was debbisecting "r-cran-git2r" to see when exactly
bug #1084352 was fixed.

In this case, the only difference between "last bad" and "first good"
was the source package version being built, but not the list
of installed packages.

If the list of installed packages is what the error refers to,
I don't think that's an error of "should never happen" kind,
so I would consider that as a bug in my modified script.

Maybe also a bug in the original debbisect script, but I'm not sure,
so feel free to ask me to report it separately.

Thanks.

[Santiago Vila]

Hi.

I found another place requiring small changes:

Time is always supposed to go forward, so the message
about changed packages should be more like this:

- print(
- "the following packages differ between the last good and "
- "first bad timestamp:"
- )
+ order1, order2 = ("bad", "good") if staticargs.reverse else ("good", "bad")
+ print(f"the following packages differ between the last {order1} and first {order2} timestamp:")

and the output which follows should also be changed because otherwise
this is what it may happen:

libgsettings-qt-dev:amd64 1.0.0-2 -> 1.0.0-1+b1
libgsettings-qt1:amd64 1.0.0-2 -> 1.0.0-1+b1
linux-libc-dev 6.12.17-1 -> 6.12.16-1

that's weird because the arrow (->) represents time which is better
to consider as always going forward.

Thanks.