Re: [PATCH v3 0/2] cvsimport: add test illustrating a bug in cvsps

On Wed, Mar 18, 2009 at 11:22:43AM -0700, Junio C Hamano was talking about:

Heiko Voigt [off-list ref] writes:

quoted

This is an updated version of the first patch and an addition to ensure
correct handling of branches in fixes. 

I've already merged the first one to 'next' so this needs to be turned
into an incremental update if we were to continue building on top in the
git project.

I however have a bigger issue with this, perhaps because I do not have the
feeling that I fully understand where these patches are going.

To explain my intentions a little more: I recently imported a huge
repository with ~11 years of history from a RCS based system. 

The final step into git land was through CVS. Here I really struggled to
find the right tool and it costed me quite some time just to find a
robust tool for the job (and to figure out why the "standard" tool
failed). 

So my main goal is to save some time and hassle for everyone else going
this route. There are really nicer things to spend time on than
importing and repairing RCS files.

I think many people when starting with git get the feeling: Oh look at
this SHA1 based database and stuff these people have written a really
neat robust system. Then you look at getting your history (from CVS)
into it and it becomes a nightmare. The command git cvsimport just does
not fit with the rest of the git tools quality.

Your approach seems to me to:

 - add tests to git test suite that expose issues the current cvsimport
   that runs on an unpatched cvsps has;

 - diagnose and fix

   - the issues in cvsimport, if the problem is because cvsimport is
     mishandling correct output from cvsps; or

   - the issues in cvsps (and adjust cvsimport to patched cvsps if
     necessary), if the problem is because output from cvsps is incorrect.

That all feels sane, and having the tests to verify the end result would
help the people who collaborate on these tasks.

But how much of the actual fix will be made to cvsps, and how much to
cvsimport? 

I can not answer this question at the moment. One thing would be fixing
cvsps, which just for one test (mine) seems like a lot of work. I
haven't even looked into the other issues.

After writing my last email it came to my mind that it could be a
simpler approach to take parsecvs (only because its already written in C
otherwise probably cvs2svn/cvs2git) and change the interface so it
matches the one of git cvsimport and integrate it with git.

To let this happen the question is how important various features of the
current cvsimport are:

  * incremental import

  * keyword substitution

  * ...

If the majority of the changes are to happen on cvsps (which
is not unexpected, given that many people who tried and wrote various cvs
importers put blame on the shortcomings of its output), I am afraid that
it would not help majority of git users until the fixes to cvsps that come
out of this effort hit their distros for me to keep these tests in the
git.git repository.  I do not build and install custom cvsps (because I
haven't had to work with complex history in CVS that your improvements to
cvsps are need to deal with correctly), and I suspect many others are in
the same boat.  In addition, if your tests are in the git.git repository,
they need to say test_expect_success for people with patched cvsps and
test_expect_failure for people without, and because I suspect that the
majority of git developers do not run bleeding edge cvsps, it does not do
anything but slowing down the test suite.

It feels as if you are scratching my feet through my shoes while I still
am wearing them.  I wonder if it would be more direct and simpler approach
to add tests to cvsps and handle these improvements as part of the cvsps
maintenance/development effort, not as part of cvsimport fixes, at least
initially.

I think it is great that you started actively working on identifying and
fixing issues with cvsps, that many others have gave up and gone to
different avenues, and I certainly do not mind keeping the new tests in
'pu' for wider exposure, in order to make it easier for other people who
use cvsimport and want to collaborate with you improving it through
improving cvsps.

But I am starting to think that it was a mistake on my part to have merged
the initial set of tests to 'next'.

Thoughts?

In the long run I think at least a basic test for the current issues
should be in git.  Otherwise if cvsimport gets fixed you do not have a
way of making sure all tools (cvsps) in their right versions are
installed. Even with another non cvsps importer this property needs to
be ensured to handle non trivial repositories.
 
The only people who actually need to know about issues in cvsimport are
the ones who are trying to get away from CVS. So its probably best to
disable the "advanced" tests and have an environment variable e.g.:
"ALL_CVSIMPORT_TESTS" for enabling them.

cheers Heiko