Ugly, not fully working (see TODO) example of patches rediff tool.

diff --git a/rediff-patches.py b/rediff-patches.py
new file mode 100755 (executable)
index 0000000..4b5bdaf
--- /dev/null
+++ b/rediff-patches.py
@@ -0,0 +1,78 @@
+#!/usr/bin/python3
+
+# rediff-patches.py name.spec
+
+# TODO:
+# - handle rediff of last patch (need some way to terminate build just after that patch is applied)
+# - or maybe apply patches on our own instead of using rpmbuild for that
+# - argparse fro arguments
+# - cleanup
+
+import os
+import re
+import rpm
+import shutil
+import subprocess
+import sys
+import tempfile
+
+RPMBUILD_ISPATCH = (1<<1)
+
+def unpack(spec, builddir, until_patch=None):
+    cmd = [ 'rpmbuild', '-bp', '--define',  '_builddir %s' % builddir ]
+    if until_patch is not None:
+        cmd += [ '--define', '%%patch%d exit; #' % until_patch ]
+    cmd += [ spec ]
+    subprocess.check_call(cmd, stdout=sys.stderr, stderr=sys.stderr, timeout=600)
+
+def diff(diffdir_org, diffdir, builddir, output):
+    diffdir_org = os.path.basename(diffdir_org)
+    diffdir = os.path.basename(diffdir)
+
+    with open(output, 'wt') as f:
+        cmd = [ 'diff', '-urNp', '-x', '*.orig', diffdir_org, diffdir ]
+        try:
+            subprocess.check_call(cmd, cwd=builddir, stdout=f, stderr=sys.stderr, timeout=600)
+        except subprocess.CalledProcessError as err:
+            if err.returncode != 1:
+                raise
+
+specfile = sys.argv[1]
+
+tempdir = tempfile.TemporaryDirectory(dir="/dev/shm")
+topdir = tempdir.name
+builddir = os.path.join(topdir, 'BUILD')
+
+rpm.addMacro("_builddir", builddir)
+
+r = rpm.spec(specfile)
+
+patches = {}
+
+for (name, nr, flags) in r.sources:
+    if flags & RPMBUILD_ISPATCH:
+        patches[nr] = name
+
+applied_patches = {}
+re_patch = re.compile(r'^%patch(?P<patch_number>\d+)\w*(?P<patch_args>.*)')
+for line in r.parsed.split('\n'):
+    m = re_patch.match(line)
+    if not m:
+        continue
+    patch_nr = int(m.group('patch_number'))
+    patch_args = m.group('patch_args')
+    applied_patches[patch_nr] = patch_args
+
+appsourcedir = rpm.expandMacro("%{_sourcedir}")
+appbuilddir = rpm.expandMacro("%{_builddir}/%{?buildsubdir}")
+
+for (patch_nr, patch_name) in sorted(patches.items()):
+    if patch_nr not in applied_patches:
+        continue
+    print("*** patch %d: %s" % (patch_nr, patch_name), file=sys.stderr)
+    unpack(specfile, builddir, patch_nr)
+    os.rename(appbuilddir, appbuilddir + ".org")
+    unpack(specfile, builddir, patch_nr + 1)
+    diff(appbuilddir + ".org", appbuilddir, builddir, os.path.join(topdir, os.path.join(appsourcedir, patch_name + ".rediff")))
+    shutil.rmtree(builddir)
+tempdir.cleanup()