Add downgrade functionality (contributed script)

.gitignore

@@ -6,12 +6,13 @@
 *.pyproj
 *.sln
 
-# Logs and databases #
+# Headphones files #
 ######################
 *.log
 *.db*
 *.db-journal
 *.ini
+version.lock
 logs/*
 cache/*
 
@@ -64,6 +65,3 @@ _ReSharper*/
 /logs
 .project
 .pydevproject
-
-
-headphones_docs

contrib/downgrade.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+
+# Parameter check
+if [ -z "$1" ] || [ -z "$2" ]; then
+    echo "Syntax: $0 <source directory> <data directory>"
+    exit 1
+fi
+
+# Repository check
+if [ ! -d "$1/.git" ]; then
+    echo "This script can only downgrade Headphones installations via Git."
+    exit 1
+fi
+
+# Version file check
+if [ ! -s "$2/version.lock" ]; then
+    echo "Missing the version.lock file in the data folder, or the file is empty. Did you start Headphones at least once?"
+    exit 1
+fi
+
+# Git installation check
+if [ ! -x "$(command -v wget)" ]; then
+    echo "Git is required to downgrade."
+    exit 1
+fi
+
+# Display information
+HASH=$(cat $2/version.lock)
+
+echo "This script will try to downgrade Headphones to the last version that started, version $HASH. Make sure you have a backup of your config file and database, just in case!"
+echo "Press enter to continue, or CTRL + C to quit."
+read
+
+# Downgrade
+cd "$1"
+git reset --hard "$HASH"
+
+echo "All done, Headphones should be downgraded to the last version that started."

headphones/__init__.py

@@ -138,9 +138,8 @@ def initialize(config_file):
         if not os.path.exists(CONFIG.CACHE_DIR):
             try:
                 os.makedirs(CONFIG.CACHE_DIR)
-            except OSError:
-                logger.error(
-                    'Could not create cache dir. Check permissions of datadir: %s', DATA_DIR)
+            except OSError as e:
+                logger.error("Could not create cache dir '%s': %s", DATA_DIR, e)
 
         # Sanity check for search interval. Set it to at least 6 hours
         if CONFIG.SEARCH_INTERVAL < 360:
@@ -154,10 +153,23 @@ def initialize(config_file):
         except Exception as e:
             logger.error("Can't connect to the database: %s", e)
 
-        # Get the currently installed version - returns None, 'win32' or the git hash
-        # Also sets INSTALL_TYPE variable to 'win', 'git' or 'source'
+        # Get the currently installed version. Returns None, 'win32' or the git
+        # hash.
         CURRENT_VERSION, CONFIG.GIT_BRANCH = versioncheck.getVersion()
 
+        # Write current version to a file, so we know which version did work.
+        # This allowes one to restore to that version. The idea is that if we
+        # arrive here, most parts of Headphones seem to work.
+        if CURRENT_VERSION:
+            version_lock_file = os.path.join(DATA_DIR, "version.lock")
+
+            try:
+                with open(version_lock_file, "w") as fp:
+                    fp.write(CURRENT_VERSION)
+            except IOError as e:
+                logger.error("Unable to write current version to file '%s': %s",
+                    version_lock_file, e)
+
         # Check for new versions
         if CONFIG.CHECK_GITHUB_ON_STARTUP:
             try: