ENH: Allow no bullet point framgents and file templating

[seberg]

This adds a single file mode to allow creating a single file for
each release. It also allows to disable automatic indentation of
bullet point items, since not all projects necessarily use
bullet points for release notes. In single file mode, the output
file is a format string of the name, version, and project_date
and the file is fully replaced (start_line is not supported).

name, version, and project_date are now available in the main
template, allowing to render the title there. To make this useful,
the title_format should be set to false.

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Will create a newsfragment soon. Is this something you would like? Basically, I would like to be able to create most of our current numpy style release notes automatically (for example: https://github.com/numpy/numpy/blob/master/doc/release/1.17.0-notes.rst).

[seberg]

Sorry, also needs lots of test of course, although wouldn't mind a quick getting back on that.

[seberg]

Just noticed that gh-147 does the title part already nicely. Probably nicer since versioninfo.name is more elegant. I think that one breaks backward compatibility if no title_format is given? Which I do not mind too much.

Anyway, happy to pull this out or do the opposite, but I would very much appreciate if we can try to keep things moving here @hawkowl? I expect other projects may have similar needs as NumPy.

[codecov-io]

Codecov Report

Merging #158 into master will decrease coverage by 2.32%.
The diff coverage is 55.55%.

@@            Coverage Diff             @@
##           master     #158      +/-   ##
==========================================
- Coverage    90.3%   87.98%   -2.33%     
==========================================
  Files          11       11              
  Lines         392      416      +24     
  Branches       69       78       +9     
==========================================
+ Hits          354      366      +12     
- Misses         22       28       +6     
- Partials       16       22       +6

Impacted Files	Coverage Δ
src/towncrier/build.py	85.71% <100%> (ø)	⬆️
src/towncrier/_settings.py	95.55% <33.33%> (-4.45%)	⬇️
src/towncrier/_builder.py	92% <56.52%> (-8%)	⬇️

---

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[hawkowl]

@seberg Hi! I finished off #147, would you be able to rebase the other changes?

[seberg]

Thanks so much, I will do that today or tomorrow!

[seberg]

OK, assuming the existing tests pass, this now adds two things (slight modification from before):

1. single_file = false option. If given, the output filename can be specified using the same formatting as the (old-style) title_format. In that case the file is always overwritten.
2. no_bullets = true option. If given, towncrier will not assume that all fragments should be rendered as bullet points (which means indenting them, plus the - already being in the template). Since I think it might (during the development) happen that we mix bullets and non bullets, I decided to sort fragments starting with bullet points to the front for the moment.

(this may still settle a bit, but should be good to look at.)

[seberg]

Can I ping you on this? Being able to handle non-bullet points is pretty important to me. The single file per release I could probably handle differently. I do not mind taking a different approach here though or fixing things up a bit more.

[seberg]

Oone more gentle ping @hawkowl, I do not mind working a bit more here though.

[hawkowl]

@seberg I cherry picked out the single file changes into another branch, and I'll poke at some tests for them.

I don't quite understand the bullet point fragments, though, since making entries bulletpoints or not is the responsibility of the template. Could you just make an example output of what the option lets you do that editing the template doesn't? I can't quite figure it out from the code.

[seberg]

Thanks. Making it bullet points or not should be the responsibility of the template, the issue is that the code (not the template) does indenting by two spaces (this could be done in the jinja2 template in a similar manner, but is not). In NumPy our snipplets normally have a subheading:

Deprecations
============

Deprecate `np.alen`
  -------------------
  `np.alen` was deprecated. Use `len` instead. (`gh-14181 <https://github.com/numpy/numpy/pull/14181>`__)

and the above is how it gets rendered by towncrier, note the spaces of the following lines which are not in the original) fragment.

Since we sometimes also use bullet points (Sections where everything is short), I thought I may want to allow both, and just sort the bullet points to the top, to be cleaned up manually before the final release (which is the reason for the sorting changes). I can work without the sorting change, although I doubt there is much harm in it.

[seberg]

Sorry that I never updated this (if this can go in some way or another). Rebased onto master.

[hawkowl]

Thanks! I added some tests and merged it in here: #162

[seberg]

Thank you so much!