Merge branch 'es/rebase-i-no-abbrev'

The commit object names in the insn sheet that was prepared at the beginning of "rebase -i" session can become ambiguous as the rebasing progresses and the repository gains more commits. Make sure the internal record is kept with full 40-hex object names. * es/rebase-i-no-abbrev: rebase -i: fix short SHA-1 collision t3404: rebase -i: demonstrate short SHA-1 collision t3404: make tests more self-contained