logging.bash: Add dedcat and excat helpers

scripts/hashwalker

@@ -14,7 +14,7 @@ Usage:  $0 BRANCH_A UPSTREAM_BRANCH [START_REFSPEC]
 Note:  Commit hashes are walked along UPSTREAM_BRANCH.
 EOUSAGE
 
-[ -z "$1" -o -z "$2" ] && errcat "$usage" && exit 1
+[ -z "$1" -o -z "$2" ] && dedcat "$usage"
 
 branch_a="$1"
 upstream_branch="$2"

scripts/include_info

@@ -41,7 +41,7 @@ get-incl() {
 cc=${CC:-cc}
 cxx=${CXX:-cxx}
 
-[ -z "$1" ] && errcat "$usage" && exit 1
+[ -z "$1" ] && dedcat "$usage"
 
 case "$1" in
   'clang') ;&
@@ -72,8 +72,7 @@ while getopts 'cpP' opt; do
       sort -u <<<$(get-both)
       ;;
     *)
-      errcat "$usage"
-      exit 1
+      dedcat "$usage"
       ;;
   esac
 done