Add build script for letsencrypt-auto.

Change template language to reference files, saving me some boilerplate over the dict-based .format() thing I originally had in mind.

Put newlines at the ends of bootstrap scripts. It makes the built le-auto script prettier.

letsencrypt_auto/build.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+"""Stitch together the letsencrypt-auto script.
+
+Implement a simple templating language in which {{ some/file }} turns into the
+contents of the file at ./pieces/some/file.
+
+"""
+from os.path import dirname, join
+import re
+from sys import argv
+
+
+def main():
+    dir = dirname(argv[0])
+
+    def replacer(match):
+        rel_path = match.group(1)
+        with open(join(dir, 'pieces', rel_path)) as replacement:
+            return replacement.read()
+
+    with open(join(dir, 'letsencrypt-auto.template')) as template:
+        result = re.sub(r'{{\s*([A-Za-z0-9_./-]+)\s*}}',
+                        replacer,
+                        template.read())
+    with open(join(dir, 'letsencrypt-auto'), 'w') as out:
+        out.write(result)
+
+
+if __name__ == '__main__':
+    main()

letsencrypt_auto/letsencrypt-auto.template

@@ -49,13 +49,13 @@ DeterminePythonVersion() {
   fi
 }
 
-{{bootstrap_deb_common}}
-{{bootstrap_rpm_common}}
-{{bootstrap_suse_common}}
-{{bootstrap_arch_common}}
-{{bootstrap_gentoo_common}}
-{{bootstrap_free_bsd}}
-{{bootstrap_mac}}
+{{ bootstrappers/deb_common.sh }}
+{{ bootstrappers/rpm_common.sh }}
+{{ bootstrappers/suse_common.sh }}
+{{ bootstrappers/arch_common.sh }}
+{{ bootstrappers/gentoo_common.sh }}
+{{ bootstrappers/free_bsd.sh }}
+{{ bootstrappers/mac.sh }}
 
 # Install required OS packages:
 Bootstrap() {
@@ -180,7 +180,7 @@ elif [ "$1" != "--_skip-to-install" ]; then
     # There is no $ interpolation due to quotes on heredoc delimiters.
     set +e
     TEMP_DIR=`$PYTHON - << "UNLIKELY_EOF"
-{{download_upgrade}}
+{{ download_upgrade.py }}
 UNLIKELY_EOF`
     DOWNLOAD_STATUS=$?
     set -e
@@ -205,11 +205,11 @@ else  # --_skip-to-install was passed.
   TEMP_DIR="$2"
   shift 2
   cat << "UNLIKELY_EOF" > $TEMP_DIR/letsencrypt-auto-requirements.txt
-{{requirements}}
+{{ letsencrypt-auto-requirements.txt }}
 UNLIKELY_EOF
 
   cat << "UNLIKELY_EOF" > $TEMP_DIR/peep.py
-{{peep}}
+{{ peep.py }}
 UNLIKELY_EOF
 
   set +e