docker: switch to Alpine Linux for the master image

Relates to https://github.com/shaarli/Shaarli/issues/843

Changed:
- switch base image from Debian:Jessie to Alpine:3.6
- switch to PHP 7.1
- switch from supervisord to s6 to manage services

See:
- https://alpinelinux.org/
- https://wiki.alpinelinux.org/wiki/Nginx_with_PHP
- http://www.skarnet.org/software/s6/
  - http://www.skarnet.org/software/s6/s6-svscan.html
  - http://www.skarnet.org/software/s6/s6-svc.html
  - http://www.skarnet.org/software/s6/s6-svstat.html

Signed-off-by: VirtualTam <virtualtam@flibidi.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index a3696ec9..656c27b0 100644
--- a/Makefile
+++ b/Makefile
@@ -115,7 +115,7 @@ check_permissions:
         @echo "----------------------"
         @echo "Check file permissions"
         @echo "----------------------"
-        @for file in `git ls-files`; do \
+        @for file in `git ls-files | grep -v docker`; do \
                 if [ -x $$file ]; then \
                         errors=true; \
                         echo "$${file} is executable"; \