Add built-in citation support using new citeproc library.

This deprecates the use of the external pandoc-citeproc
filter; citation processing is now built in to pandoc.

* Add dependency on citeproc library.
* Add Text.Pandoc.Citeproc module (and some associated unexported
  modules under Text.Pandoc.Citeproc).  Exports `processCitations`.
  [API change]
* Add data files needed for Text.Pandoc.Citeproc:  default.csl
  in the data directory, and a citeproc directory that is just
  used at compile-time.  Note that we've added file-embed as a mandatory
  rather than a conditional depedency, because of the biblatex
  localization files. We might eventually want to use readDataFile
  for this, but it would take some code reorganization.
* Text.Pandoc.Loging: Add `CiteprocWarning` to `LogMessage` and use it
  in `processCitations`. [API change]
* Add tests from the pandoc-citeproc package as command tests (including
  some tests pandoc-citeproc did not pass).
* Remove instructions for building pandoc-citeproc from CI and
  release binary build instructions.  We will no longer distribute
  pandoc-citeproc.
* Markdown reader: tweak abbreviation support.  Don't insert a
  nonbreaking space after a potential abbreviation if it comes right before
  a note or citation.  This messes up several things, including citeproc's
  moving of note citations.
* Add `csljson` as and input and output format. This allows pandoc
  to convert between `csljson` and other bibliography formats,
  and to generate formatted versions of CSL JSON bibliographies.
* Add module Text.Pandoc.Writers.CslJson, exporting `writeCslJson`. [API
  change]
* Add module Text.Pandoc.Readers.CslJson, exporting `readCslJson`. [API
  change]
* Added `bibtex`, `biblatex` as input formats.  This allows pandoc
  to convert between BibLaTeX and BibTeX and other bibliography formats,
  and to generated formatted versions of BibTeX/BibLaTeX bibliographies.
* Add module Text.Pandoc.Readers.BibTeX, exporting `readBibTeX` and
  `readBibLaTeX`. [API change]
* Make "standalone" implicit if output format is a bibliography format.
  This is needed because pandoc readers for bibliography formats put
  the bibliographic information in the `references` field of metadata;
  and unless standalone is specified, metadata gets ignored.
  (TODO: This needs improvement. We should trigger standalone for the
  reader when the input format is bibliographic, and for the writer
  when the output format is markdown.)
* Carry over `citationNoteNum` to `citationNoteNumber`.  This was just
  ignored in pandoc-citeproc.
* Text.Pandoc.Filter: Add `CiteprocFilter` constructor to Filter.
  [API change] This runs the processCitations transformation.
  We need to treat it like a filter so it can be placed
  in the sequence of filter runs (after some, before others).
  In FromYAML, this is parsed from `citeproc` or `{type: citeproc}`,
  so this special filter may be specified either way in a defaults file
  (or by `citeproc: true`, though this gives no control of positioning
  relative to other filters).  TODO: we need to add something to the
  manual section on defaults files for this.
* Add deprecation warning if `upandoc-citeproc` filter is used.
* Add `--citeproc/-C` option to trigger citation processing.
  This behaves like a filter and will be positioned
  relative to filters as they appear on the command line.
* Rewrote the manual on citatations, adding a dedicated Citations
  section which also includes some information formerly found in
  the pandoc-citeproc man page.
* Look for CSL styles in the `csl` subdirectory of the pandoc user data
  directory.  This changes the old pandoc-citeproc behavior, which looked
  in `~/.csl`.  Users can simply symlink `~/.csl` to the `csl`
  subdirectory of their pandoc user data directory if they want
  the old behavior.
* Add support for CSL bibliography entry formatting to LaTeX, HTML,
  Ms writers.  Added CSL-related CSS to styles.html.

2 files changed, 43 insertions, 4 deletions

diff --git a/data/templates/default.latex b/data/templates/default.latex
index d6cca9c98..31327c1d8 100644
--- a/data/templates/default.latex
+++ b/data/templates/default.latex
@@ -368,10 +368,25 @@ $endif$
 $if(csl-refs)$
 \newlength{\cslhangindent}
 \setlength{\cslhangindent}{1.5em}
-\newenvironment{cslreferences}%
-  {$if(csl-hanging-indent)$\setlength{\parindent}{0pt}%
-  \everypar{\setlength{\hangindent}{\cslhangindent}}\ignorespaces$endif$}%
-  {\par}
+\newlength{\csllabelwidth}
+\setlength{\csllabelwidth}{3em}
+\newenvironment{CSLReferences}[3] % #1 hanging-ident, #2 entry sp
+ {% don't indent paragraphs
+  \setlength{\parindent}{0pt}
+  % turn on hanging indent if param 1 is 1
+  \ifodd #1 \everypar{\setlength{\hangindent}{\cslhangindent}}\ignorespaces\fi
+  % set line spacing
+  % set entry spacing
+  \ifnum #2 > 0
+  \setlength{\parskip}{#3\baselineskip}
+  \fi
+ }%
+ {}
+\usepackage{calc} % for \widthof, \maxof
+\newcommand{\CSLBlock}[1]{#1\hfill\break}
+\newcommand{\CSLLeftMargin}[1]{\parbox[t]{\maxof{\widthof{#1}}{\csllabelwidth}}{#1}}
+\newcommand{\CSLRightInline}[1]{\parbox[t]{\linewidth}{#1}}
+\newcommand{\CSLIndent}[1]{\hspace{\cslhangindent}#1}
 $endif$
 
 $if(title)$
diff --git a/data/templates/styles.html b/data/templates/styles.html
index b179d4871..3d7ebb55d 100644
--- a/data/templates/styles.html
+++ b/data/templates/styles.html
@@ -121,3 +121,27 @@ $endif$
 $if(displaymath-css)$
 .display.math{display: block; text-align: center; margin: 0.5rem auto;}
 $endif$
+$if(csl-css)$
+div.csl-bib-body { }
+div.csl-entry {
+  clear: both;
+$if(csl-entry-spacing)$
+  margin-bottom: $csl-entry-spacing$;
+$endif$
+}
+.hanging div.csl-entry {
+  margin-left:2em;
+  text-indent:-2em;
+}
+div.csl-left-margin {
+  min-width:2em;
+  float:left;
+}
+div.csl-right-inline {
+  margin-left:2em;
+  padding-left:1em;
+}
+div.csl-indent {
+  margin-left: 2em;
+}
+$endif$