[CentOS] rpm - diff and patch updating

[Les Mikesell]

Frank Cox wrote:
> I am attempting to create a rpm of the latest version of a program.  The
> rpm for the previous version contains a number of patch files that make
> numerous changes various files in the tar.gz as downloaded from the
> project's website so it will work properly on Linux.
> 
> The latest version of the program has changed enough stuff that some of
> the patches now fail to apply.  "1 out of 1 hunk FAILED" and so on.
> Upon comparing the previous version's files to the latest version, I see
> that the problem is that some of the files that need to be patched have
> had some stuff moved around a bit, just enough to (apparently) cause
> patch to fail.
> 
> By way of experimentation, I manually changed one of the files in the
> new version to match what the patch says it should be, then created a
> new patch file from that and it applies and appears to work fine.  (I
> patched the previous version's file, compared the result to the original
> and made the same change in the new version's file.)
> 
> This method seems to work fine when the change is only one or two lines,
> but some of the patches are somewhat more involved than that.
> 
> It seems to me that there may be an automated way to handle this matter
> by somehow patching a into b, then compare a and b and make
> corresponding changes in c.  Basically the same process that I just
> tried manually on a small patch file, without all of the labour and
> chance of a screw-up that would be involved in manually comparing the
> old files and rewriting the new file.
> 
> I have two questions:
> 
> First, am I going about this the right way?  And if so, is there a way
> to automate the process as described in the previous paragraph?
> 
> Second, what is the proper convention for handling this in a rpm?  The
> obvious solution seems to be to create new patch files and throw the old
> ones away, then build the rpm from that.  Some of these patches appear
> to go back several versions, though, so is there a better or more proper
> way to handle this than just throwing them out and making a whole new
> set of patches?
> 
> I have learned a lot more about patch and diff tonight than I ever
> needed to know before.  Very cool stuff, and very useful.

You probably can't automate this - but note that many of the patches included in 
RHEL/CentOS RPMs are to backport fixes from newer versions of the code without 
bringing in new/different features.  So, if you start with newer base code you 
may not need many/most of the patches at all.

-- 
    Les Mikesell
     lesmikesell at gmail.com