[development] Getting rid of core hacks for drupal upgrade to happen. Need tips on the process.

[Dipen]

Hi,

 I have started working on a large code base built using drupal 5.2 and now
there is a requirement to upgrade it to 5.22 and eventually 6. The problem
is that lot of core files (modules, include folder) was hacked over a period
of last 1 year to make drupal work according to req, and things were
obviously not done drupal way. I am working on identifying changes that were
made to core and then would attempt on implementing those changes from a
custom module, reverting the core to 5.2 clean state. The job would have
been easier if source control management was used from start in the project,
but that did not happen and hacks were made before SCM started recording
them and hence I can not rely on svn history. What I am doing right now is
the following:

1> I have downloaded drupal 5.2 for reference.
2> Have trunk of tainted project checked out.
3> Diffing module files one by one ( against 5.2 download in step 1, so
diffing hacked node.module against 5.2 node.module) and recording changes to
find out what changes were intended when the developer hacked the core (eg.
node module file)

For 3 to happen, I can write a script to get diff of all files in say
includes folder, but that would give me just the diff file and it would be
hard to study why were the changes done. But I am sure I can use it as a
starting tool to find out which files have changed in core when measured
against cleand drupal 5.2 and then focus on those files.

I wanted suggestions and tips on:

1> Apart from svn history, diffing files one by one, does any one have
suggestions to find out changes between hacked and clean file? Maybe at a
folder level? Like diff the whole include folder or diff the whole modules
folder. (I know about beyond compare, anything else?)

2> Any tips, experiences, suggestions on the process of removing core hacks
and implementing them outside of core.

3> Any suggestions on the whole approach? If it can be made more efficient.

I would like opinion of anyone who has dealt with core hacks and removed
them to clear upgrade path.

Thanks
Dipen
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