Mailsplit

I thought I would use "git mailsplit" to split a mbox file (which downloaded 
from public inbox) so that I could attemp to resurrect a patch series for from 
a year ago.  

The motivation is that I downloaded the series [1] and applied to a tag from 
about the time period that the patch was sent out [2].  

The "git am -3 patch.mbox  quit 2/3 of the way though.   I resolved the fix. 
and ran "git am --continue" which didn't apply the rest of the patches in the 
mbox.

So two questions:
1)  why would git version 2.18.0 not appear to continue applying the patches.   

2) where do I find the command "git mailsplit".   The onlything in my 
installed tree is:

	$ find  /usr/local/ -name '*mailsplit*'
	/usr/local/share/doc/git-doc/git-mailsplit.txt
	/usr/local/share/doc/git-doc/git-mailsplit.html
	/usr/local/share/man/man1/git-mailsplit.1
	/usr/local/libexec/git-core/git-mailsplit

sps

[1] https://public-inbox.org/git/1502914591-26215-1-git-send-email-martin@mail.zuhause/

[2] I wanted to make sure that I could apply back then before attempting to 
either apply to the latest git version or rebase to the latest git version.