How do you squash commits into one patch with git format-patch?

I'd recommend doing this on a throwaway branch as follows. If your commits are in the "newlines" branch and you have switched back to your "master" branch already, this should do the trick:

[adam@mbp2600 example (master)]$ git checkout -b tmpsquash
Switched to a new branch "tmpsquash"

[adam@mbp2600 example (tmpsquash)]$ git merge --squash newlines
Updating 4d2de39..b6768b2
Fast forward
Squash commit -- not updating HEAD
 test.txt |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

[adam@mbp2600 example (tmpsquash)]$ git commit -a -m "My squashed commits"
[tmpsquash]: created 75b0a89: "My squashed commits"
 1 files changed, 2 insertions(+), 0 deletions(-)

[adam@mbp2600 example (tmpsquash)]$ git format-patch master
0001-My-squashed-commits.patch

Just to add one more solution to the pot: If you use this instead:

git format-patch master --stdout > my_new_patch.diff

Then it will still be 8 patches... but they'll all be in a single patchfile and will apply as one with:

git am < my_new_patch.diff

As you already know, a git format-patch -8 HEAD will give you eight patches.

If you want your 8 commits appear as one, and do not mind rewriting the history of your branch (o-o-X-A-B-C-D-E-F-G-H), you could :

git rebase -i
// squash A, B, C, D, E ,F, G into H

or, and it would be a better solution, replay all your 8 commits from X (the commit before your 8 commits) on a new branch

git branch delivery X
git checkout delivery
git merge --squash master
git format-patch HEAD

That way, you only have one commit on the "delivery" branch, and it represent all your last 8 commits

I always use git diff so in your example, something like

git diff master > patch.txt