alpine packaging: build packages and base image directly from git

Currently, we tar up the git repo before building alpine packages.
This ensures that the packages we're building are exactly what is
checked in.  But, in practice, this restriction causes us to not
be able to build off of git contexts, which is a convenient feature
especially when using docker-compose.

So, here, we build the alpine packages directly from the contents
of the current directory and we install the packages into a base
image to ease downstream consumption.  There is still work to be
done in that area, as we need to package up the daemons, frr user
and all the rest, but that's for later...

Testing-done:

Built directly from the git repo, built from a reference to the
git repo and built using docker-compose, all seemed to work.  Also,
tested by @leleobhz and seems to build fine.

Thanks to Leonardo Amaral (@leleobhz) for reporting the issue and for
the original idea for a fix.

Issue: https://github.com/FRRouting/frr/issues/2024
Signed-off-by: Arthur Jones <arthur.jones@riverbed.com>

.dockerignore

@@ -0,0 +1 @@
+.git

doc/developer/building-frr-on-alpine.rst

@@ -34,26 +34,38 @@ This will put the apk packages in:
 Usage
 -----
 
-To add the packages to a docker image, create a Dockerfile in ./docker/pkgs:
+To create a base image with the frr packages installed:
 
 ::
 
-   FROM alpine:3.7
-   RUN mkdir -p /pkgs
-   ADD apk/ /pkgs/
-   RUN apk add --no-cache --allow-untrusted /pkgs/x86_64/*.apk
+   docker build --rm -f docker/alpine/Dockerfile -t frr:latest .
 
-And build a docker image:
+Or, if you don't have a git checkout of the sources, you can build a base
+image directly off the github account:
 
 ::
 
-   docker build --rm --force-rm -t alpine-dev-pkgs:latest docker/pkgs
+   docker build --rm -f docker/alpine/Dockerfile -t frr:latest \
+	https://github.com/frrouting/frr.git
 
-And run the image:
+And to run the image:
 
 ::
 
-   docker run -it --rm alpine-dev-pkgs:latest /bin/sh
+   docker run -it --rm frr:latest /bin/sh
 
 Currently, we only package the raw daemons and example files, so, you'll
 need to run the daemons by hand (or, better, orchestrate in the Dockerfile).
+
+We can also build directly from docker-compose, with a docker-compose.yml file
+like this one:
+
+::
+
+   version: '2.2'
+
+   services:
+      frr:
+         build:
+            context: https://github.com/frrouting/frr.git
+            dockerfile: docker/alpine/Dockerfile

docker/.gitignore

@@ -1,2 +1 @@
-src.tar
 pkgs/

docker/alpine/Dockerfile

@@ -12,8 +12,7 @@ RUN apk add --no-cache abuild acct alpine-sdk attr autoconf automake bash \
     patch pax-utils pcre perl pkgconf python2 python2-dev readline \
     readline-dev sqlite-libs squashfs-tools sudo tar texinfo xorriso xz-libs \
     groff gzip bc py-sphinx
-RUN mkdir -p /src
-ADD src.tar /src
+ADD . /src
 RUN (cd /src && \
 	./bootstrap.sh && \
 	./configure \
@@ -22,9 +21,13 @@ RUN (cd /src && \
 	make dist)
 FROM alpine:3.7 as alpine-builder
 RUN apk add --no-cache abuild alpine-sdk && mkdir -p /pkgs/apk
-ADD alpine-build.sh /usr/bin/
-ADD builder /etc/sudoers.d
+ADD docker/alpine/alpine-build.sh /usr/bin/
+ADD docker/alpine/builder /etc/sudoers.d
 COPY --from=source-builder /src/*.tar.gz /src/alpine/APKBUILD /dist/
 RUN adduser -D -G abuild builder && chown -R builder /dist /pkgs
 USER builder
 RUN /usr/bin/alpine-build.sh
+FROM alpine:3.7
+RUN mkdir -p /pkgs/apk
+COPY --from=alpine-builder /pkgs/apk/ /pkgs/apk/
+RUN apk add --no-cache --allow-untrusted /pkgs/apk/x86_64/*.apk

docker/alpine/build.sh

@@ -9,12 +9,8 @@ set -x
 ##
 c=`git rev-parse --short=10 HEAD`
 commit=`printf '%u\n' 0x$c`
-git archive --format=tar $c > docker/alpine/src.tar
-(cd docker/alpine && \
-	docker build --build-arg commit=$commit --rm --force-rm -t \
-		frr:alpine-$c . && \
-	rm -f src.tar)
-
+docker build -f docker/alpine/Dockerfile \
+	--build-arg commit=$commit -t frr:alpine-$c .
 id=`docker create frr:alpine-$c`
 docker cp ${id}:/pkgs/ docker
 docker rm $id