upgrade alpine base image to v3.15.0 (see below)

https://git.alpinelinux.org/aports/commit/main/netcat-openbsd?h=3.15-stable&id=2fccbad32270c6f49fda5fa3611be40d434cd9c1

https://github.com/fphammerle/docker-borgbackup-client/commit/04610b728c8ec3c83f7618b1641aabb97b3346af

Dockerfile

@@ -1,7 +1,7 @@
-FROM docker.io/alpine:3.14.3
+FROM docker.io/alpine:3.15.0
 
 ARG DUMB_INIT_PACKAGE_VERSION=1.2.5-r1
-ARG NETCAT_PACKAGE_VERSION=1.130-r2
+ARG NETCAT_PACKAGE_VERSION=1.130-r3
 ARG DMA_REPOSITORY=http://dl-cdn.alpinelinux.org/alpine/edge/testing
 ARG DMA_PACKAGE_VERSION=0.13-r2
 RUN apk add --no-cache \

dumb-init-package-log.url

@@ -1 +1 @@
-https://git.alpinelinux.org/aports/log/community/dumb-init
+https://git.alpinelinux.org/aports/log/community/dumb-init?h=3.15-stable

netcat-openbsd-package-log.url

@@ -0,0 +1 @@
+https://git.alpinelinux.org/aports/log/main/netcat-openbsd?h=3.15-stable