Make reldst optional

No need to bug everybody with relsrc/reldst

src/include/release.sh

     #
     local rlevel=$1
     local newtag
+    local reldst
 
     _relck git_present
     _relck at_relsrc
     debug_var newtag
     $MKIT_DRY && return
     git tag -m "$(ini 1value project:name) $newtag - $CODENAME" "$newtag"
-    git branch -f "$(ini 1value project:reldst)" "$newtag"
+
+    reldst=$(ini 1value project:reldst)
+    debug_var reldst
+    if test -n "$reldst";
+    then
+        git branch -f "$reldst" "$newtag"
+    fi
 }
 
 _vbump() {