How can I format patch with what I stash away

Sure, git stash show supports this:

git stash show -p

So, use

git stash list

to find out the number of the stash that you want to export as a patch, then

git stash show -p stash@{<number>} > <name>.patch

to export it.

For example:

git stash show -p stash@{3} > third_stash.patch

This answer provides info about both saving the patch and applying it where you want to use it.

To stash the output in a file:

 git stash show -p --color=never > my-patch-name.patch

Verify patch looks good:

git apply --stat my-patch-name.patch

Verify no errors:

git apply --check my-patch-name.patch

Apply the patch

git apply my-patch-name.patch

Use

$> git stash list
stash@{0}: WIP on master: 84fx31c Merged with change to /public/
stash@{1}: WIP on master: 463yf85 FlupResource: also takes json as a query parameter

to get a list of your recently stashed stuff. Git actually creates commit objects when you stash.

They are commits like everything else. You can check them out in a branch:

$> git checkout -b with_stash stash@{0}

You can then publish this branch and you colleague can merge or cherry-pick that commit.

Above solutions won't work for binary data. The following add support for it:

git stash show stash@{0} -p --binary

Edit

Note: I just wanted to add a comment to above replies but my reputation is not sufficient.