GIT_SEQUENCE_EDITOR=true runs autosquash rebases without opening the interactive editor

git rebase -i --autosquash normally opens $GIT_EDITOR even when every line in the todo list is pick or fixup, blocking automation. Setting GIT_SEQUENCE_EDITOR=true (or :) makes git use the no-op true command as the sequence editor, which exits zero and accepts the autogenerated todo list as-is. This lets git commit --fixup=<sha> + autosquash be composed in non-interactive scripts and agent contexts.

For non-interactive autosquash workflows, prefix rebase invocations with GIT_SEQUENCE_EDITOR=true, e.g. GIT_SEQUENCE_EDITOR=true git rebase -i --autosquash <base>~1.