Warnings repeated during backups prevent completion and log files grow rapidly.

[wyylg]

• error message

  Command output:

  [WARN] ignoring error reading parent snapshot: RusticError(ArchiverError(TreeStackEmpty))
  [WARN] ignoring error reading parent snapshot: RusticError(ArchiverError(TreeStackEmpty))
  [WARN] ignoring error reading parent snapshot: RusticError(ArchiverError(TreeStackEmpty))
  [WARN] ignoring error reading parent snapshot: RusticError(ArchiverError(TreeStackEmpty))
  [WARN] ignoring error reading parent snapshot: RusticError(ArchiverError(TreeStackEmpty))
  ...
  

  Log:

  [WARN] ignoring error: RusticError(Ignore(UnableToOpenFile { file: "C:\\Users\\user\\AppData\\Roaming\\Mozilla\\Firefox\\Profiles\\XXXXXXXX.default-release\\parent.lock", source: Os { code: 32, kind: Uncategorized, message: "Another program is using this file and the process is inaccessible." } }))
  [WARN] ignoring error reading parent snapshot: RusticError(ArchiverError(TreeStackEmpty))
  ...
  

• environment
  Windows10, rustic v0.9.3

  Partial configurations:

  [[backup.snapshots]]
  sources = [
    'C:\Users\user\AppData\Roaming\Mozilla\Firefox',
    # 'C:\Users\user\AppData\Roaming\rustic',
  ]
  

• my checks

  I executed the backup command without error before modifying the configuration file, and now I try to troubleshoot the configuration item, and I find that this warning is preceded by another warning in the logs ("UnableToOpenFile"). When I close the Firefox program, the error no longer appears when performing a backup. Not only that, but it seems that other files in use will have this error and the backup cannot be completed.