[Rd] suggestion for R >= 3.0: computer-readable CHANGELOG

[Philippe Grosjean]

Hello,

Here are a few questions that would be useful to get an answer via 
dedicated functions in utils or tools packages:
- When did function foo appeared in R or in a given package?
- When did argument myarg appeared in function foo?
- When did function bar get deprecated or when did it disappeared?
- I wrote a script using functions foo and bar with R 1.9.1. My script 
does not work any more with current version. What were all the changes 
made to foo and/or to bar since then (this could obviously help me to 
update my script for current R version)?

Currently, we have to read NEWS (or perhaps a non official changelog) 
manually to get such answers.

The basic function to retrieve data that would answer to these questions 
would be something like:

 > changes(c("foo", "bar"))

That function could, for instance, read information in a 
computer-readable file named CHANGELOG... because the problem is there! 
Changes are currently recorded in NEWS, but ONLY in a human-readable 
form! A quick suggestion for a format for CHANGELOG by example:

Date       Object   Action  Value   Message
2009-04-17 package  commit  1.1-0   Enhanced version of my package
2009-04-15 foo      add     foo(y)  New function foo in my package
2009-04-14 bar      debug           bar(NULL) returned wrong result
2009-04-01 package  commit  1.0-0   First version of package on CRAN

It should be kept simple. May be an "Author" field in the records would 
be nice too. Also a function to record a new entry in the CHANGELOG 
could look like:

 > track("XXX", action = "debug", message = "my comment", file = 
"/somewhere/CHANGELOG")

The file NEWS would not change and should be kept to present the same 
information in a human-readable format.

Also, a function that lists all functions used in a script or a package 
(Romain François is working in this direction with svTools package), 
plus a function to plot one or several "changes" objects as returned by 
changes() on a time axis or "version axis" would be welcome additions to 
further track and plot evolution of R, or of R packages for a group of 
functions of interest. Finally, a function to easily record the 
dependences used and their versions in a script would complete the set 
of tools.

These 4-5 functions are not difficult to write (although I suspect that 
this simplistic proposal would become more complex if one consider to 
interact with subversion, to separate development and release versions, 
...). But to be really useful, they should be better designed and 
proposed by the R core team, and included in the official specifications 
for writing package. May I suggest to think about such a change for R 
version 3.0?

Things get more complicated for verifying CHANGELOG in R CMD check. At 
least, one could check actions like:
- object or function addition, deprecation or disappearance,
- argument changes in functions, slot changes in objects,
- function refactoring (change in the code from previous version)
but only if we provide also the previous version of a package to R CMD 
check.

I would be happy to contribute, but the concept must certainly be 
further discussed and enhanced (here?), and then, accepted by the R core 
team before going any further.

All the best,

Philippe Grosjean
-- 
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( ( ( ( (    Prof. Philippe Grosjean
  ) ) ) ) )
( ( ( ( (    Numerical Ecology of Aquatic Systems
  ) ) ) ) )   Mons-Hainaut University, Belgium
( ( ( ( (
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