Sphinx's copyright substitution currently allows years identified as
the current year to be downgraded to previous years when
``SOURCE_DATE_EPOCH`` is configured, to assist reproducibility [1] of
documentation builds.
However, we have a test case ``test_html_multi_line_copyright``,
written in 2024, that mentioned a future year (2025).
Now that we have reached 2025, it is eligible for substitution when
``SOURCE_DATE_EPOCH`` is configured. Many buildsystems, such as those
used by Debian and Fedora, choose the most-recent packaging/commit
timestamp to use as `SOURCE_DATE_EPOCH`'s timestamp, since those
correspond sensibly to a time-of-build.
However, for the Sphinx 8.1.3 release including the updated
substitution logic, the year-of-release/commit was 2024. Thus, if a
commit/packaging date from that year is chosen, and
``SOURCE_DATE_EPOCH`` is configured when the unit tests run, the
``test_html_multi_line_copyright`` test will fail.
The fix suggested here is to explicitly unset ``SOURCE_DATE_EPOCH``
within ``test_html_multi_line_copyright``.
[1]: https://www.reproducible-builds.org/
Authored-by: Colin Watson <cjwatson@debian.org>
Co-authored-by: Colin Watson <cjwatson@debian.org>
Authored-by: James Addison <55152140+jayaddison@users.noreply.github.com>
Co-authored-by: James Addison <55152140+jayaddison@users.noreply.github.com>
Only substitute copyright notice years with values from
``SOURCE_DATE_EPOCH`` for entries that match the current
system clock year, and disallow substitution of future years.
Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>
