add a scrollback flavour to st, which adds the following patch to the build:

https://st.suckless.org/patches/scrollback/st-scrollback-0.8.5.diff

ok jung@ (maintainer, who also pointed out the existence of a separate
program https://tools.suckless.org/scroll/, though it seems to me this is
something of a failed experiment, jan@ agrees)

x11/Makefile

@@ -288,6 +288,7 @@
      SUBDIR += spice-gtk
      SUBDIR += sselp
      SUBDIR += st
+     SUBDIR += st,scrollback
      SUBDIR += stalonetray
      SUBDIR += stumpwm
      SUBDIR += swarp

x11/st/Makefile

@@ -2,6 +2,8 @@ COMMENT=		simple X terminal
 
 V=			0.9
 DISTNAME=		st-${V}
+SUPDISTFILES=		st-scrollback-0.8.5.diff:0
+REVISION=		0
 
 CATEGORIES=		x11
 
@@ -13,9 +15,10 @@ MAINTAINER=		Joerg Jung <jung@openbsd.org>
 PERMIT_PACKAGE=	Yes
 
 # uses pledge()
-WANTLIB=		X11 Xft c fontconfig freetype m util z
+WANTLIB=		X11 Xft c fontconfig freetype m util
 
 MASTER_SITES=		https://dl.suckless.org/st/
+MASTER_SITES0=		https://st.suckless.org/patches/scrollback/
 
 MAKE_ENV=		LDFLAGS="${LDFLAGS}" \
 			X11INC=${X11BASE}/include \
@@ -23,6 +26,14 @@ MAKE_ENV=		LDFLAGS="${LDFLAGS}" \
 
 NO_TEST=		Yes
 
+FLAVORS=		scrollback
+FLAVOR?=
+
+.if ${FLAVOR:Mscrollback}
+PATCHFILES=		${SUPDISTFILES}
+.endif
+PATCH_DIST_STRIP=	-p1
+
 do-install:
 	${INSTALL_PROGRAM} ${WRKBUILD}/st ${PREFIX}/bin/
 	${INSTALL_MAN} ${WRKSRC}/st.1 ${PREFIX}/man/man1/

x11/st/distinfo

@@ -1,2 +1,4 @@
 SHA256 (st-0.9.tar.gz) = 82NZeZc06ueFvss3QGPwvoM88i+ItPFpzSUbmTJOCOc=
+SHA256 (st-scrollback-0.8.5.diff) = 3H9SI7JvyBPZHUrjW9qlTWMCTK6fGK/Zs1lLozmd+lU=
 SIZE (st-0.9.tar.gz) = 48171
+SIZE (st-scrollback-0.8.5.diff) = 8914

x11/st/pkg/DESCR

@@ -1 +1,5 @@
 st is a simple virtual terminal emulator for X which sucks less.
+
+Flavour:
+	scrollback - allows scrolling through terminal output with
+			shift+pgup/pgdn