Factor Go source file listing into a script

scripts/list_harmony_go_files.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+exec git ls-files '*.go' | grep -v \
+	-e '^vendor/' \
+	-e '\.pb\.go$' \
+	-e '/mock_stream\.go' \
+	-e '/host_mock\.go' \
+	-e '/gen_[^/]*\.go'

scripts/travis_checker.sh

@@ -27,12 +27,7 @@ trap 'case "${tmpdir}" in ?*) rm -rf "${tmpdir}";; esac' EXIT
 tmpdir=$(mktemp -d)
 
 go_files="${tmpdir}/go_files.txt"
-git ls-files '*.go' | grep -v \
-	-e '^vendor/' \
-	-e '\.pb\.go$' \
-	-e '/mock_stream\.go' \
-	-e '/host_mock\.go' \
-	-e '/gen_[^/]*\.go' > "${go_files}"
+"${progdir}/list_harmony_go_files.sh" > "${go_files}"
 
 # Print dirname of each relative pathname from stdin (one per line).
 dirnames() {