Description of problem:
Some of the programs provided by the patchutils package may invoke `patch`, but the package does not depend on the patch package:

$ yum deplist patchutils
Last metadata expiration check: 0:03:55 ago on Mon Jul 30 21:21:11 2018.
package: patchutils-0.3.4-10.fc28.x86_64
  dependency: /bin/bash
   provider: bash-4.4.23-1.fc28.x86_64
  dependency: /bin/sh
   provider: bash-4.4.23-1.fc28.x86_64
  dependency: /usr/bin/perl
   provider: perl-interpreter-4:5.26.2-412.fc28.x86_64
  dependency: libc.so.6(GLIBC_2.14)(64bit)
   provider: glibc-2.27-30.fc28.x86_64
  dependency: perl(Getopt::Std)
   provider: perl-interpreter-4:5.26.2-412.fc28.x86_64
  dependency: rtld(GNU_HASH)
   provider: glibc-2.27-30.fc28.i686
   provider: glibc-2.27-30.fc28.x86_64

Version-Release number of selected component (if applicable):
See above.

How reproducible:
I believe but am not certain that you can get `combinediff` to invoke `patch` if you provide it with two patches operating on the same file.  You can see it in the source here:  https://github.com/twaugh/patchutils/blob/3c70aa137ad8c4ea9085a73c0dbc1c6897b6ad45/src/interdiff.c#L839

Additional info:
In Debian, patchutils does indeed depend on patch.  https://packages.debian.org/buster/patchutils