Better handling of \part in LaTeX.

Closes #1905.

Removed stateChapters from ParserState.

Now we parse chapters as level 0 headers, and parts as level -1 headers.
After parsing, we check for the lowest header level, and if it's
less than 1 we bump everything up so that 1 is the lowest header level.
So `\part` will always produce a header; no command-line options
are needed.

1 files changed, 30 insertions, 0 deletions

diff --git a/test/command/1905.md b/test/command/1905.md
new file mode 100644
index 000000000..744d1c4d9
--- /dev/null
+++ b/test/command/1905.md
@@ -0,0 +1,30 @@
+```
+% pandoc -f latex-auto_identifiers -t html
+\chapter{chapone}
+\part{partone}
+\chapter{chaptwo}
+\section{secone}
+^D
+<h2>chapone</h2>
+<h1>partone</h1>
+<h2>chaptwo</h2>
+<h3>secone</h3>
+```
+
+```
+% pandoc -f latex-auto_identifiers -t html
+\chapter{chapone}
+\chapter{chaptwo}
+\section{secone}
+^D
+<h1>chapone</h1>
+<h1>chaptwo</h1>
+<h2>secone</h2>
+```
+
+```
+% pandoc -f latex-auto_identifiers -t html
+\section{secone}
+^D
+<h1>secone</h1>
+```