squash commits deep down in history

Hi,

i need to squash several commits into a single one in a automated way. I know that there is interactive rebase, which can also be automated using GIT_SEQUENCE_EDITOR. Unfortunately my history is very large and i need to squash deep down in the history several times. So using interactive rebase seems not to be the right tool.

I wonder if i can solve this task using filter-branch? I have a file that list the SHA1s for each squash operation per line. All SHA1s of a line are in chronological order (youngest to oldest), or in other words: the first SHA1 is the child of the second, and so on.

| ab4423e 3432343 3234252
| 2324342 5232343
| ...

Lets say there are N lines in that file. Each line means: squash all SHA1s of this line into the first (or last) SHA1 of this line. Performing this task with rebase would require N rewritings of the history. So e.g. HEAD (but many others too) would be rewritten N times even if it is not directly part of a line. My thinking is, that a filter-branch can do this in a single rewrite and therefore would be much more performant.

How can i solve this? Any ideas?

Best regards Henning