How to use git interactive rebase for signing off a series of commits

Question

I would like to sign off all commits on a branch that I have finished and want to send to an upstream project (e.g. via a pull request on GitHub).

A recommended way I've found is to use

git rebase -i [base-commit]
# Set all commits to "edit"
git commit --amend --signoff  # do this for all commits

How can I do this automatically, in one non-interactive command?

Answer 1

With Git 2.13 (Q2 2017), no more "git commit --amend --signoff" needed:
See commit 9f79524 (18 Apr 2017), and commit 0fb3c4f, commit b7cc705 (15 Apr 2017) by Giuseppe Bilotta (Oblomov).
^{(Merged by Junio C Hamano -- gitster -- in commit 768c7cb, 26 Apr 2017)}

rebase: pass --[no-]signoff option to git am

This makes it easy to sign off a whole patchset before submission.

The git rebase man page now includes:

--signoff:

This flag is passed to 'git am' to sign off all the rebased commits.
Incompatible with the --interactive option.

---

Update (one year later, May 2018) "git rebase" has learned to honor "--signoff" option when using backends other than "am" (but not "--preserve-merges").

rebase: extend --signoff support

Allow --signoff to be used with --interactive and --merge.
In interactive mode only commits marked to be picked, edited or reworded will be signed off.

The main motivation for this patch was to allow one to run 'git rebase --exec "make check" --signoff' which is useful when preparing a patch series for publication and is more convenient than doing the signoff with another --exec command.

This change also allows --root without --onto to work with --signoff as well (--root with --onto was already supported).

It is also more robust:

rebase -p: error out if --signoff is given

rebase --preserve-merges does not support --signoff so error out rather than just silently ignoring it so that the user knows the commits will not be signed off.

Answer 2

It turns that git aliases can do this quite nicely. Put into your ~/.gitconfig:

[alias]
  # Usage: git signoff-rebase [base-commit]
  signoff-rebase = "!GIT_SEQUENCE_EDITOR='sed -i -re s/^pick/e/' sh -c 'git rebase -i $1 && while git rebase --continue; do git commit --amend --signoff --no-edit; done' -"

Here's also a Gist for it.

You use it just like git rebase; the picks are automatically flipped to edits using sed and --no-edit makes sure to not open an editor for every single commit.