UI/updater: Improved handling of failure conditions

Currently if a file is partially written to (eg, the file is opened for
writing but the write fails), the updater won't correctly roll back to the
previous version, leaving the OBS install in an inconsistent state.

We now track failed installs or hash failures on patched files with a new
STATE_INSTALL_FAILED state and properly roll back on errors.

UI/win-update/updater/updater.cpp

@@ -238,6 +238,7 @@ enum state_t {
 	STATE_PENDING_DOWNLOAD,
 	STATE_DOWNLOADING,
 	STATE_DOWNLOADED,
+	STATE_INSTALL_FAILED,
 	STATE_INSTALLED,
 };
 
@@ -296,7 +297,8 @@ struct update_t {
 
 	void CleanPartialUpdate()
 	{
-		if (state == STATE_INSTALLED) {
+		if (state == STATE_INSTALL_FAILED ||
+			state == STATE_INSTALLED) {
 			if (!previousFile.empty()) {
 				DeleteFile(outputPath.c_str());
 				MyCopyFile(previousFile.c_str(),
@@ -823,6 +825,8 @@ static bool UpdateFile(update_t &file)
 			return false;
 		}
 
+		file.previousFile = oldFileRenamedPath;
+
 		int  error_code;
 		bool installed_ok;
 
@@ -839,6 +843,8 @@ static bool UpdateFile(update_t &file)
 					Status(L"Update failed: Couldn't "
 					       L"verify integrity of patched %s",
 					       curFileName);
+
+					file.state = STATE_INSTALL_FAILED;
 					return false;
 				}
 
@@ -848,6 +854,8 @@ static bool UpdateFile(update_t &file)
 					       L"check of patched "
 					       L"%s failed",
 					       curFileName);
+
+					file.state = STATE_INSTALL_FAILED;
 					return false;
 				}
 			}
@@ -872,11 +880,12 @@ static bool UpdateFile(update_t &file)
 				       L"(error %d)",
 				       curFileName,
 				       GetLastError());
+
+			file.state = STATE_INSTALL_FAILED;
 			return false;
 		}
 
-		file.previousFile = oldFileRenamedPath;
-		file.state        = STATE_INSTALLED;
+		file.state = STATE_INSTALLED;
 	} else {
 		if (file.patchable) {
 			/* Uh oh, we thought we could patch something but it's
@@ -890,6 +899,8 @@ static bool UpdateFile(update_t &file)
 		 * make sure they exist */
 		CreateFoldersForPath(file.outputPath.c_str());
 
+		file.previousFile = L"";
+
 		bool success = !!MyCopyFile(
 				file.tempPath.c_str(),
 				file.outputPath.c_str());
@@ -897,11 +908,11 @@ static bool UpdateFile(update_t &file)
 			Status(L"Update failed: Couldn't install %s (error %d)",
 					file.outputPath.c_str(),
 					GetLastError());
+			file.state = STATE_INSTALL_FAILED;
 			return false;
 		}
 
-		file.previousFile = L"";
-		file.state        = STATE_INSTALLED;
+		file.state = STATE_INSTALLED;
 	}
 
 	return true;