[Reproducible-builds] Bug#814057: Add option to ignore mtime and ctime in report

[Leo Famulari]

Source: diffoscope
Severity: wishlist

Dear Maintainer,

It would be helpful if users could instruct diffoscope to not report
different mtimes and ctimes in the files being inspected.

Here is my use case:

I am hunting down some non-determinism in the python-2.7 package in GNU
Guix. Our build system installs all the outputs of the build process in
one directory. I make a copy of that directory, erase the source of the
copy, rebuild, make a second copy, and then use diffoscope to compare
the copies.

Since I am comparing the entire output of Python 2.7's build process,
there are a lot of files, and they *all* have different ctimes (we set
mtimes to epoch).

The resulting diffoscope HTML report is 41 megabytes, and I would guess
that 99% of it is reporting the different ctimes. It takes a while to
sift through this noise to find the real problems, and loading the file
threatens the health of my web browser ;)

BTW, I am using diffoscope-34, provided by Guix, although I don't think
this affects the validity of my request.

PS— My apologies if this report is formatted improperly. It's my first
time submitting a bug to Debian via email (reportbug did not work out of
the box).

-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.3.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to en_US.UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)