[beast] TRAVIS: applyenv: allow importing arbitrary environment variables into Dockerfile

[Tim Janik <timj src gnome org>]

commit 09ff5d25d316343d1af5616dfcc611eb09b67794
Author: Tim Janik <timj gnu org>
Date:   Mon Mar 21 20:58:03 2016 +0100

    TRAVIS: applyenv: allow importing arbitrary environment variables into Dockerfile
    
    We use applyenv to pass build context into Dockerfile. In particular, this makes
    the FROM distribution configurable and transports build settings like http_proxy
    or the travis job number into the docker command context.
    
    Signed-off-by: Tim Janik <timj gnu org>

 .travis.docker |    7 +++++--
 .travis.yml    |    9 ++++-----
 buildtool.sh   |   30 +++++++++++++++++++++++++++---
 3 files changed, 36 insertions(+), 10 deletions(-)
---
diff --git a/.travis.docker b/.travis.docker
index fe7b708..b31903d 100644
--- a/.travis.docker
+++ b/.travis.docker
@@ -2,10 +2,13 @@
 
 # Pick distribution to start from
 FROM @XFROM@
-
-# Maintainer information and contact information
 MAINTAINER Tim Janik <timj gnu org>
+
+# Carry over enviroment variables
 ENV EMAIL beast gnome org
+ENV TRAVIS_JOB_NUMBER "@TRAVIS_JOB_NUMBER@"
+ENV http_proxy "@http_proxy@"
+ENV RAPICORNREPO "@RAPICORNREPO@"
 
 # Automation tools and convenience commands
 ENV DEBIAN_FRONTEND noninteractive
diff --git a/.travis.yml b/.travis.yml
index 3b3266d..103aa59 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,7 +13,7 @@ matrix:
 
 env:
   global:
-    - http_proxy=""
+    #- http_proxy="http://example.com";
     - bintray_url="https://dl.bintray.com/beast-team";
   matrix:
     - XFROM="ubuntu:wily"   XUP="wily"
@@ -30,10 +30,9 @@ before_install:
 install:
   # Complete history is required for VCSREVISION
   - travis_retry git fetch --unshallow
-  # Configure Dockerfile
-  - RAPICORNREPO="$bintray_url/$XUP snapshot main" && \
-    sed -e "s&@XFROM@&$XFROM&""g" -e "s&@RAPICORNREPO@&$RAPICORNREPO&""g" \
-        -e "${http_proxy:+/^FROM\b/aENV http_proxy $http_proxy}" < .travis.docker > Dockerfile
+  # Configure Dockerfile by substituting @VAR@ with $VAR
+  - export RAPICORNREPO="$bintray_url/$XUP snapshot main" && \
+    ./buildtool.sh applyenv .travis.docker > Dockerfile
   # Build and run tests, create packages
   - docker build -t beast .
 
diff --git a/buildtool.sh b/buildtool.sh
index 843605a..30bcf07 100755
--- a/buildtool.sh
+++ b/buildtool.sh
@@ -6,7 +6,7 @@ SCRIPTNAME=`basename $0`;
 function die { e="$1" ; shift ; [ -n "$*" ] && echo "$SCRIPTNAME: $*" >&2 ; exit "${e:-127}" ; } # die 
<exitcode> [message]
 
 # == config ==
-mkconfig()     # print shell variables describing package, version, commit id, monotonic revision
+mkconfig() # print shell variables describing package, version, commit id, monotonic revision
 {
   set -e # abort on errors
   # ensure we're in the project directory and have full git history
@@ -43,9 +43,9 @@ mkconfig()    # print shell variables describing package, version, commit id, monot
   popd >/dev/null                                      # cd OLDPWD
 }
 
-
 # == bintrayup ==
-bintrayup() {
+bintrayup() # Usage: bintrayup <bintrayaccount> <packagepath> <packagedistribution> [packages...]
+{
   set +x # avoid printing authentication secrets
   mkconfig >/dev/null # PACKAGE, VERSION, ...
   ACCNAME="$1"; PKGPATH="$2"; PKGDIST="$3" # BINTRAY_APITOKEN must be set by caller
@@ -76,6 +76,30 @@ bintrayup() {
   test $ALLOK = 0 || die 2 "Some files failed to upload"
 }
 
+# == applyenv ==
+applyenv() # Usage: applyenv <inputfile> [inputargs...]
+{
+  # NOTE: avoid using unprefixed environment variables, they could become output substitutions
+  applyenv__input___="$1"; shift
+  test -r "$applyenv__input___" || { echo "$0: failed to read: $applyenv__input___"; exit 1; }
+  applyenv__sedprogram___=""
+  for applyenv__word___ in \
+    $(grep -oE '@[0123456789abcdefghijklmnopqrstuvwxyz_ABCDEFGHIJKLMNOPQRSTUVWXYZ]+@' "$applyenv__input___" 
| sort | uniq)
+  do
+    applyenv__varname___=${applyenv__word___//@/} # word= EXAMPLE@ varname=EXAMPLE
+    if [[ ${!applyenv__varname___} == *\|* ]]; then
+      echo "$0: detected '|', skipping variable: \$$applyenv__varname___" >&2
+    elif test "$applyenv__word___" == "@0@"; then
+      applyenv__sedprogram___="$applyenv__sedprogram___; s|$applyenv__word___|${applyenv__input___}|g"
+    else
+      applyenv__sedprogram___="$applyenv__sedprogram___; s|$applyenv__word___|${!applyenv__varname___}|g"
+    fi
+  done
+  sed "$applyenv__sedprogram___" "$applyenv__input___"
+}
+
+
 # == commands ==
 [[ "$1" != config ]]   || { shift; mkconfig "$@" ; exit $? ; }
 [[ "$1" != bintrayup ]]        || { shift; bintrayup "$@" ; exit $? ; }
+[[ "$1" != applyenv ]] || { shift; applyenv "$@" ; exit $? ; }