Close #871: Enable binary repository (#887)

* add my own build key
* enable the repo in the config
* update the README file
* Adjust testcase, that validates the keys and enable it in testcases_fast.sh
* Only save/load keys to/from the config file, which we ask for during
  'pmbootstrap init', so the binary repo gets used even if a config file
  already exists (this also removes a workaround, that deletes the work
  folder path from the config dictionary before writing it)
* Download missing APKINDEX.tar.gz files with Python code, before
  attempting to build packages (so we know which ones aleady exist in
  the binary packages repository)
* Consider APKINDEX files older than 4 hours as outdated and download
  them again (also in Python code)
* Provide 'pmbootstrap update' to force-update the APKINDEX files
* Travis: more logging output on failure
* Only allow keys from config_keys to be used by "pmbootstrap config"

pmb/helpers/frontend.py

@@ -35,6 +35,7 @@ import pmb.chroot.other
 import pmb.flasher
 import pmb.helpers.logging
 import pmb.helpers.other
+import pmb.helpers.repo
 import pmb.helpers.run
 import pmb.install
 import pmb.parse
@@ -114,16 +115,15 @@ def chroot(args):
 
 
 def config(args):
-    pmb.helpers.logging.disable()
-    if args.name and args.name not in pmb.config.defaults:
-        valid_keys = ", ".join(sorted(pmb.config.defaults.keys()))
-        print("The variable name you have specified is invalid.")
-        print("The following are supported: " + valid_keys)
-        sys.exit(1)
+    keys = pmb.config.config_keys
+    if args.name and args.name not in keys:
+        logging.info("NOTE: Valid config keys: " + ", ".join(keys))
+        raise RuntimeError("Invalid config key: " + args.name)
 
     cfg = pmb.config.load(args)
     if args.value:
         cfg["pmbootstrap"][args.name] = args.value
+        logging.info("Config changed: " + args.name + "='" + args.value + "'")
         pmb.config.save(args, cfg)
     elif args.name:
         value = cfg["pmbootstrap"].get(args.name, "")
@@ -131,6 +131,9 @@ def config(args):
     else:
         cfg.write(sys.stdout)
 
+    # Don't write the "Done" message
+    pmb.helpers.logging.disable()
+
 
 def index(args):
     pmb.build.index_repo(args, args.arch_native)
@@ -157,6 +160,10 @@ def menuconfig(args):
     pmb.build.menuconfig(args, args.package)
 
 
+def update(args):
+    pmb.helpers.repo.update(args, True)
+
+
 def kconfig_check(args):
     # Default to all kernel packages
     packages = args.packages