patch, 2 partsuserdiff: add support for R programming language

> This patch adds two userdiff tests for R programming language
> files. These files define a simple function, with and without
> indentation.
>
> Signed-off-by: Rodrigo Carvalho <rodrigorsdc@gmail.com>
> ---
> diff --git a/t/t4018/r-indent b/t/t4018/r-indent
> @@ -0,0 +1,6 @@
> +RIGHT <- function(a, b) {
> +    c = mean(a, b)
> +    d = c + 2
> +    ChangeMe()
> +    return (d)
> +}

> The patch appends userdiff.c file in order to support R programming
> language function header. This will be useful for those who use Git
> for versioning .R files.
> 
> Signed-off-by: Rodrigo Carvalho <rodrigorsdc@gmail.com>
> ---
>  userdiff.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/userdiff.c b/userdiff.c
> index da75625020..d1d31ea67e 100644
> --- a/userdiff.c
> +++ b/userdiff.c
> @@ -317,6 +317,10 @@ PATTERNS("python",
>  	 "|[-+0-9.e]+[jJlL]?|0[xX]?[0-9a-fA-F]+[lL]?"
>  	 "|[-+*/<>%&^|=!]=|//=?|<<=?|>>=?|\\*\\*=?"),
>  	 /* -- */
> +PATTERNS("r",

>> +	"^[ \t]*([a-zA-z][a-zA-Z0-9_.]*[ \t]*<-[ \t]*function.*)$",
>
> I wonder how useful this is in practice. Unlike C or Java for example,
> code can live outside of functions in R scripts. If you have a script
> without any functions, there would not be any hunk headers. If you have
> a script with a mix of functions and code outside of functions, the code
> after a function would be attributed to the function. I'm not saying
> that this is bad, but just asking if this is part of the plan.

>> +	/* -- */
>> +	"[a-zA-Z_][a-zA-Z0-9_.]*"),
>
> This singles out identifiers. Every single other characters would be its
> own word. I'd consider this a disimprovement. If you are not prepared to
> provide worddiff patterns, I recommend to use "[^ \t]+", which roughly
> amounts to the default behavior. It can be improved incrementally in
> later patches.

> > This singles out identifiers. Every single other characters would be its
> > own word. I'd consider this a disimprovement. If you are not prepared to
> > provide worddiff patterns, I recommend to use "[^ \t]+", which roughly
> > amounts to the default behavior. It can be improved incrementally in
> > later patches.
>
> Good point.

> > Please squash the test cases into this patch. Don't forget to test an
> > indented function, and while at it, test a function definition *nested*
> > in a function definition: that documents what the expected outcome is.
>
> Again, good point.

> The patch appends userdiff.c file in order to support R programming
> language function header. This will be useful for those who use Git
> for versioning .R files.
>
> Also, add three userdiff tests for R programming language
> files. These files define simple function and nested function,
> with and without indentation.
>
> Signed-off-by: Rodrigo Carvalho <rodrigorsdc@gmail.com>
> ---
> Changes in v2:
> - Add support for function defined by '='
> - Replace word regex to '[^ \t']
> - Add new test that handles with nested function

> Rodrigo Carvalho <rodrigorsdc@gmail.com> writes:
> 
>> The patch appends userdiff.c file in order to support R programming
>> language function header. This will be useful for those who use Git
>> for versioning .R files.
>>
>> Also, add three userdiff tests for R programming language
>> files. These files define simple function and nested function,
>> with and without indentation.
>>
>> Signed-off-by: Rodrigo Carvalho <rodrigorsdc@gmail.com>
>> ---
>> Changes in v2:
>> - Add support for function defined by '='
>> - Replace word regex to '[^ \t']
>> - Add new test that handles with nested function
> 
> Sorry, but this fell of the radar.
> 
> It seems all the reviewer comments on the previous round have been
> addressed.  If everybody is happy with this version, let's merge it
> down to 'next', for the next cycle.
> 
> Thanks.