bin/54620: patch(1) has issues with long lines

[coypu%sdf.org@localhost]

>Number:         54620
>Category:       bin
>Synopsis:       patch(1) has issues with long lines
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Oct 16 09:40:00 +0000 2019
>Originator:     coypu
>Release:        NetBSD 9.99.15
>Organization:
>Environment:
NetBSD planets 9.99.15 NetBSD 9.99.15 (GENERIC) #1: Fri Oct 11 23:50:23 IDT 2019  fly@planets:/cvs/obj/sys/arch/amd64/compile/GENERIC amd64

>Description:
Unfortunately there's a very real scenario for this happening: trying to patch JSON files in pkgsrc.

It errors like:

patch: **** malformed patch at line 5: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa


>How-To-Repeat:
Here's a test case. It works if changing 10000s to 1000s.

#!/bin/sh

printf %10s |tr " " "a" > longlines 2>/dev/null

cat << EOF > longlines.patch
--- ./longlines.orig	2019-10-16 09:25:30.667656644 +0000
+++ ./longlines
@@ -1 +1 @@
EOF

printf -- "-"%10s"\n" |tr " " "a" >> longlines.patch 2>/dev/null
printf -- "+"%10s |tr " " "b" >> longlines.patch 2>/dev/null

patch longlines < longlines.patch
>Fix: