Re: Programmatically edit the git rebase sequence?

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Matthias,

On Fri, 3 Jul 2026, Matthias Beyer wrote:

> in a recent conversation at work, the question of how to
> programmatically edit the git-rebase sequence came up.

The easiest way is probably to have the interactive rebase stop at the top
of the rebase script:

	# insert a `b` (for `break`) before the first line
	GIT_SEQUENCE_EDITOR="sed -i 1ib" git rebase -i ...

(Note that this is GNU sed syntax, with BSD/macOS sed you'll have to get a
bit creative, or write a real script and refer to it via the path.)

Then you can use a script to transform the rebase script before `git
rebase --continue`.

I frequently use this technique with LLMs because they seem to be unable
to control an interactive editor correctly.

> I have a branch that touches a number of files, adds some files and
> removes some files.
> When rebasing, I want to split all commits that touched a certain subset
> of files, for the clearity of the history.
> 
> I look at the output of
> 
>     git log master..mybranch --oneline --diff-filter=M -- "./subdir/*.rs"

Noting that the OIDs in $(git rev-parse --git-path
rebase-merge/git-rebase-todo) are expanded, you could match them via the
OIDs obtained using `rev-list` instead of `log`, to enumerate the OIDs
instead of full commit history, then turning that into some kind of regex.
Something along the lines

	regex=$(git rev-list master..mybranch --diff-filter=M -- "subdir/*.rs" |
		# read all lines, then turn newlines into `\|`
		sed ':1;$b2;N;b1;:2;s/\n/\\|/g')

	GIT_REBASE_TODO="$(git rev-parse --git-path rebase-merge/git-rebase-todo)"
	test -z "$regex" ||
	sed -i "s/^pick \($regex\)/edit \1/" $GIT_REBASE_TODO

This _should_ work, but you'll most likely want to adapt it to your
particular use cases.

Ciao,
Johannes

> 
> to find all commits in that subdir that only touched the files. All of
> these commits are to be "edit"ed.
> 
> Now I fire up `git rebase -i master` and manually(!) match the list from
> above `git-log` call and find the respective commits to edit them.
> 
> Is there a way I am not aware of to do that manual step programatically?
> Something like
> 
>     git rebase -i master --edit-commits="$(git log master..mybranch --diff-filter=M --format="%H" -- "./subdir/*.rs")"
> 
> would be convenient here, although I would understand if that is too
> much clutter for the already very heavy git CLI interface :-)
> 
> Maybe I am just not aware of the obvious solution - I would be happy to
> learn that there is already one!
> 
> Best,
> Matthias
>