On Tue, 2010-10-19 at 21:53 +0200, Johan Corveleyn wrote:
Hi devs,
In the context of the diff optimization patch I'm working on ([1]),
I'm wondering if diff4 is actually used in svn. If I look for usages
of subversion/libsvn_diff/diff4.c#svn_diff_diff4, I only come up with
tools/diff/diff4.c#main.
So: this code isn't used in the svn core itself? What's the use of the
diff4 executable in tools/diff? Is it for experimentation with that
implementation, but it never really got finalized to be taken up in
svn proper? Or am I overlooking something?
You are quite right: it is there for experimentation. I believe it is
an implementation of
http://svn.apache.org/repos/asf/subversion/trunk/notes/variance-adjusted-patching.html,
which is mentioned in our (rather old) merging functional spec, here:
http://svn.apache.org/repos/asf/subversion/trunk/notes/merge-tracking/func-spec.html#aslb-merge.
Also, tools/diff/diff4.c mentions the following description above the
copyright notice: diff4-test.c -- test driver for 3-way text merges.
Wrong filename. And test driver, what does that mean?
I corrected the filename in r1024560. Test driver indicates a program
that exercises some functionality, for the purpose of testing that
functionality.
Background: I'm working on extending my patch to work for all diff's
in svn: normal diff, diff3 and diff4 (to avoid having to special case
things only for regular diff, and the patch is just as useful for
diffX as for regular diff). I don't want to break anything, so I was
looking around for ways how to exercise that code.
Should I take diff4 into account, and if so, how can I test it?
Please do take diff4 into account, just for completeness. You don't
need to write an automatic regression test for it.
- Julian
