Pass an argument to a Git alias command

If you consider the Git Faq section "Git Aliases with argument", you could do it, but by calling git through a shell:

[alias]
        rb = "!sh -c \"git rebase -i HEAD~$1\" -"

I haven't tested it yet, but if you can pass an argument, that would be the way to do it.

A similar solution would be to use a shell function:

[alias]
        rb = "!f() { git rebase -i HEAD~$1; }; f"

Rebasing all commits since branching

If you just want to rebase all the commits that are new in your branch, since the time you branched from the parent branch, it would be easier to just have the following alias in your config:

rbi = !sh -c \"git rebase -i `git merge-base $1 HEAD`\" -

Then, if you wanted to rebase all the commits you've added to your current branch, you could simply run:

git rbi parentBranch

This approach uses an argument, but instead of having to know how many commits to go back, you just supply the branch name, and it figures out most recent commit shared between the current branch and the parent branch via git merge-base

Why this, rather than git rebase -i parentBranch

The reason you would do this rather than a straight git rebase -i parentBranch is that you might not want to deal with the merge-conflicts until a later point, or even deal with a merge-conflict in one commit, and then the same conflict on the same line in another commit. See https://stackoverflow.com/a/31036645/444610