Using Ctags in rkward

[Martin Papenberg]

> Ok, I have added that in master just now (as usual, it may be up to 24
> hours for the automated builds to catch up). Please take a look.

Thanks Thomas, this is perfect; I think it is a huge improvement for rkward!

> Finally, Martin, perhaps you could write up a mini-tutorial on setting
> up CTags inside RKWard?

Sure. A primer follows here, but I can also prepare an online tutorial 
including screenshots (if you want to include this tutorial on the 
website at some point, I can prepare one in Markdown):

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- CTags has to be installed on the local machine, on Ubuntu this for 
example as follows:

* sudo apt install exuberant-ctags

- CTags by default does not have support for the R language, but can be 
added by the user. To enable R support, we can add the following lines 
to a file ".ctags" in the home directory (if it does not exist, create it):

--langdef=R
--langmap=r:.R.r
--regex-R=/^[ \t]*"?([.A-Za-z][.A-Za-z0-9_]*)"?[ \t]*(<-|=)[ 
\t]function/\1/f,Functions/

(I got this from Fong Chun Chan's Blog here: 
https://tinyheero.github.io/2017/05/13/r-vim-ctags.html)

- In rkward, activate the Ctags plugin:

* Settings -> configure rkward -> Kate Plugins -> check "CTags"

- Now, there should be a CTags button at the botton of the main rkward 
window (next to "R Console", "Help Search" etc.). Click the button and 
go to "Index targets". Here, you can click "+ Add" to add the directory 
that should be indexed by CTags. This has to be done for each directory 
where we work with R files (however, it works recursively, so if you 
index the upper most directory, all of the directories within are 
indexed as well)

- To use CTags, define custom key bindings:

* Settings -> Configure Keyboard Shortcuts -> Action CTags

I think in R, the important actions are "Go To Definition" to jump to a 
function definition (I use CTRL-Y) and "Jump back one step" (I use CTRL-Q)

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It would be nice if anyone can test and verify that this works.

Cheers,

Martin