travis: run copr build only for the master branch

This is needed to avoid building into the @codescan/csdiff copr project
upon a push to a non-master branch.  Also, pull-requests against
a non-master branch would be excluded, but they should be rare.

Drop the -x flag from the Travis build.  That PR webhook isn't private
information but still..  It is better to not make a honeypot from all
our Travis logs.

Author: praiskup

.travis.yml

@@ -19,6 +19,7 @@ matrix:
           dist: focal
           env:
               - COPR_BUILD=yes
+          if: branch = master
 
 install:
     - sudo apt-get install cmake help2man libboost-dev libboost-filesystem-dev libboost-program-options-dev libboost-python-dev libboost-regex-dev

.travis/copr-build

@@ -1,4 +1,4 @@
-#! /bin/bash -x
+#! /bin/bash
 
 # Trigger the build in Copr (from .travis.yml)