Merge branch 'jk/blame-commit-label' into maint

"git blame HEAD -- missing" failed to correctly say "HEAD" when it tried to say "No such path 'missing' in HEAD". * jk/blame-commit-label: blame.c: fix garbled error message use xstrdup_or_null to replace ternary conditionals builtin/commit.c: use xstrdup_or_null instead of envdup builtin/apply.c: use xstrdup_or_null instead of null_strdup git-compat-util: add xstrdup_or_null helper