Merge branch 'ld/git-p4-branches-and-labels'

* ld/git-p4-branches-and-labels: git-p4: label import fails with multiple labels at the same changelist git-p4: add test for p4 labels git-p4: importing labels should cope with missing owner git-p4: cope with labels with empty descriptions git-p4: handle p4 branches and labels containing shell chars