Merge branch 'ld/p4-import-labels' into maint

Correct "git p4 --detect-labels" so that it does not fail to create a tag that points at a commit that is also being imported. * ld/p4-import-labels: git-p4: fix P4 label import for unprocessed commits git-p4: do not terminate creating tag for unknown commit git-p4: failing test for ignoring invalid p4 labels