Redirect %patch output

[Andreas Scherer]

Dear all,

I want to submit an idea for extending the %patch macro by adding support for 
the '-o' option of the patch programme.

REQUEST: Extend the %patch macro in order to support an invocation like
   %patch -p1 -P0 -o Makefile.unix

ENVIRONMENT: My system is Kubuntu 12.04 LTS with rpm 4.9.1.1-1ubuntu0.3.
For creating local packages I use Kris Deugau's debbuild script 
(https://secure.deepnet.cx/trac/debbuild) with some current patches 
(https://github.com/ascherer/debbuild-0.11.3).

USE CASE: Recently I encountered the situation with two separate source 
archives that form a single set of code files. The first introduces a 
'Makefile' (https://github.com/ascherer/cweb), the second an extended 
'Makefile.unix' (https://github.com/ascherer/cwebbin), which is the actual one 
used in the '%build' section (make -f Makefile.unix). After cleaning out the 
latter, I want to apply a patch to the original 'Makefile' in the '%prep' 
section to create 'Makefile.unix' on-the-fly, instead of shipping it in the 
second tarfile.

STATE OF RESEARCH: Curiously, my initial idea

   Patch: 0001-Makefile.unix-originates-from-Makefile.patch
   [...]
   %patch -p1 -o Makefile.unix

actually works with debbuild 0.11.3. The 'debbuild' Perl script simply 
forwards the invocation options from '%patch' to 'patch' (only eliminating the 
'-P' option for detecting the patch number).

PROBLEM: Cross-checking with rpmbuild 4.9.1.1 resulted in an error message, 
because the '-o' option is not supported in this form:
   Fehler: Unbekannte Option: -o: %patch -p1 -o Makefile.unix

WORKAROUND: Alternatively, one can replace the %patch macro with a genuine 
call to the patch programme:

   Patch0: 0001-Makefile.unix-originates-from-Makefile.patch
   [...]
   patch -p1 -i %{PATCH0} -o Makefile.unix

Note that this requires the (single) patch to be qualified with the '0' 
numeral. (Moreover, plain debbuild fails to support the %[PATCH0} macro, so a 
compatible solution for both rpmbuild and debbuild is not possible.)

PROSPECT: I have not yet tried to build 'rpmbuild' from the Github sources. As 
far as I can see, module 'build/parsePrep.c' has to be changed by adding 
support for handling the '-o' option in the 'doPatchMacro' function.

Discuss. :o)

Cheers, Andreas
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