patchuserdiff: add support for Fountain documents

> Add support for Fountain, a plain text screenplay format.  Git
> facilitates not just programming specifically, but creative writing
> in general, so it makes sense to also support other plain text
> documents besides source code.
>
> In the structure of a screenplay specifically, scenes are roughly
> analogous to functions, in the sense that it makes your job easier
> if you can see which ones were changed in a given range of patches.
>
> More information about the Fountain format can be found on its
> official website, at http://fountain.io .
>
> Signed-off-by: Zoë Blade <zoe@bytenoise.co.uk>
> ---

>  Documentation/gitattributes.txt | 2 ++
>  t/t4018-diff-funcname.sh        | 1 +
>  t/t4018/fountain-scene          | 4 ++++
>  userdiff.c                      | 2 ++
>  4 files changed, 9 insertions(+)
>  create mode 100644 t/t4018/fountain-scene
>
> diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
> index 81fe586..e3b1de8 100644
> --- a/Documentation/gitattributes.txt
> +++ b/Documentation/gitattributes.txt
> @@ -527,6 +527,8 @@ patterns are available:
>  
>  - `fortran` suitable for source code in the Fortran language.
>  
> +- `fountain` suitable for Fountain documents.
> +
>  - `html` suitable for HTML/XHTML documents.
>  
>  - `java` suitable for source code in the Java language.
> diff --git a/t/t4018-diff-funcname.sh b/t/t4018-diff-funcname.sh
> index 1dbaa38..67373dc 100755
> --- a/t/t4018-diff-funcname.sh
> +++ b/t/t4018-diff-funcname.sh
> @@ -31,6 +31,7 @@ diffpatterns="
>  	cpp
>  	csharp
>  	fortran
> +	fountain
>  	html
>  	java
>  	matlab
> diff --git a/t/t4018/fountain-scene b/t/t4018/fountain-scene
> new file mode 100644
> index 0000000..6b3257d
> --- /dev/null
> +++ b/t/t4018/fountain-scene
> @@ -0,0 +1,4 @@
> +EXT. STREET RIGHT OUTSIDE - DAY
> +
> +CHARACTER
> +You didn't say the magic phrase, "ChangeMe".
> diff --git a/userdiff.c b/userdiff.c
> index 2ccbee5..5316b48 100644
> --- a/userdiff.c
> +++ b/userdiff.c
> @@ -35,6 +35,8 @@ IPATTERN("fortran",
>  	  * they would have been matched above as a variable anyway. */
>  	 "|[-+]?[0-9.]+([AaIiDdEeFfLlTtXx][Ss]?[-+]?[0-9.]*)?(_[a-zA-Z0-9][a-zA-Z0-9_]*)?"
>  	 "|//|\\*\\*|::|[/<>=]="),
> +PATTERNS("fountain", "^((INT|EST|EXT)?\\.[A-Z0-9' -]+)$",
> +	 "[^ \t-]+"),
>  PATTERNS("html", "^[ \t]*(<[Hh][1-6][ \t].*>.*)$",
>  	 "[^<>= \t]+"),
>  PATTERNS("java",

> * Although uppercase is recommended for Scene Headings to increase
>   readability, it is not required.
> 
> * A line beginning with any of the following, followed by either a
>   dot or a space, is considered a Scene Heading (unless the line is
>   preceded by an exclamation point !). Case insensitive.
> 
>      INT
>      EXT
>      EST
>      INT./EXT
>      INT/EXT
>      I/E
> 
> * You can "force" a Scene Heading by starting the line with a
>   single period.
> 
> * Scene Headings can optionally be appended with Scene
>   Numbers. Scene numbers are any alphanumerics (plus dashes and
>   periods), wrapped in #.
> 
> So, it appears wrong to insist on capital letters in the patterns.
> The pattern in the patch does not even accept punctuations on the
> line other than apostrophe.  I won't judge if it is OK to limit to
> US-ASCII ;-)
> 
> IPATTERNS("fountain",
>    "^([.][^.]|(INT|EXT|EST|INT./EXT|INT/EXT|I/E)[. ]",
>    "[^ \t-]+"),
> 
> or something like this, perhaps?