how to most effectively cherry pick by selective patch hunk?

["Robert P. J. Day" <rpjday@crashcourse.ca>]

  (i'm looking for a solution not just for current git but, sadly,
going back to git-2.9.2, which is installed on my current contract
build system, and i have little authority to bump it up.)

  summary: made a couple dozen commits on branch, call it "oldb",
where i was relatively undisciplined about enforcing clean, modular
commits so i want to go back and clean things up -- refactor by
changing order, combining some trivial commits into one, breaking
large, unwieldy commits into smaller pieces, better commit messages
and so on, so i start a new branch "newb" at the same origin, and
here's the problem.

  every old commit consisted of adding a new patch to an existing
openembedded recipe, so every commit had two components:

  * a brand new patch file to be placed under "files/", and
  * adding a new line to SRC_URI variable, as in:

    SRC_URI += " \
	first.patch \
	second.patch \
	third.patch \
	... etc etc ...
    "

  i think you see the problem. a commit adding a brand new file will
never create a merge conflict, as it's a new file. but if i start
reordering commits, then the addition of that line to the .bbappend
file will *certainly* conflict as the patches will almost certainly be
renamed and in a different order.

  what would be great is some sort of "-p" (patch selection) option
with cherry-pick, but i don't see that.

  what would work for me is to auto-get the addition of the patch file
from the old branch, at which point i am more than happy to manually
fix the .bbappend file and manually do another commit. i'm thinking i
can just "git checkout" the new patch file from the old branch, and
take it from there.

  thoughts? am i overthinking this?

rday