Merge branch 'jk/show-branch-lift-name-len-limit' into maint

"git show-branch" expected there were only very short branch names in the repository and used a fixed-length buffer to hold them without checking for overflow. * jk/show-branch-lift-name-len-limit: show-branch: use skip_prefix to drop magic numbers show-branch: store resolved head in heap buffer show-branch: drop head_len variable