Do not store downloaded file if it is already attached

[koppor]

Follow-up to #6174

When a user downloads a PDF - and this PDF equals to an already attached PDF, it should not be attached again.

Possible steps:

1. default.pdf exists
2. Download as default (1).pdf.
3. Check if file content of default.pdf equals file content of default (1).pdf (Use https://guava.dev/releases/21.0/api/docs/com/google/common/io/Files.html#equal-java.io.File-java.io.File-)
4. If it is equal, just delete default (1).pdf. Show notification that already linked. Finish.
5. If not equal, add to linked files.

[github-actions]

This issue has been inactive for half a year. Since JabRef is constantly evolving this issue may not be relevant any longer and it will be closed in two weeks if no further activity occurs.

As part of an effort to ensure that the JabRef team is focusing on important and valid issues, we would like to ask if you could update the issue if it still persists. This could be in the following form:

• If there has been a longer discussion, add a short summary of the most important points as a new comment (if not yet existing).
• Provide further steps or information on how to reproduce this issue.
• Upvote the initial post if you like to see it implemented soon. Votes are not the only metric that we use to determine the requests that are implemented, however, they do factor into our decision-making process.
• If all information is provided and still up-to-date, then just add a short comment that the issue is still relevant.

Thank you for your contribution!

[koppor]

This issue is still relevant.

@Article{ALHashemy2020,
  author    = {Rageed Hussein AL{-}Hashemy and Sadiq A. Mehdi},
  journal   = {J. Intell. Syst.},
  title     = {A New Algorithm Based on Magic Square and a Novel Chaotic System for Image Encryption},
  year      = {2020},
  number    = {1},
  pages     = {1202--1215},
  volume    = {29},
  bibsource = {dblp computer science bibliography, https://dblp.org},
  biburl    = {https://dblp.org/rec/journals/jois/AL-HashemyM20.bib},
  doi       = {10.1515/jisys-2018-0404},
  file      = {:ALHashemy2020 - A New Algorithm Based on Magic Square and a Novel Chaotic System for Image Encryption (1).pdf:PDF},
}

Then

Then

@Article{ALHashemy2020,
  author    = {Rageed Hussein AL{-}Hashemy and Sadiq A. Mehdi},
  journal   = {J. Intell. Syst.},
  title     = {A New Algorithm Based on Magic Square and a Novel Chaotic System for Image Encryption},
  year      = {2020},
  number    = {1},
  pages     = {1202--1215},
  volume    = {29},
  bibsource = {dblp computer science bibliography, https://dblp.org},
  biburl    = {https://dblp.org/rec/journals/jois/AL-HashemyM20.bib},
  doi       = {10.1515/jisys-2018-0404},
  file      = {:ALHashemy2020 - A New Algorithm Based on Magic Square and a Novel Chaotic System for Image Encryption (2).pdf:PDF;:ALHashemy2020 - A New Algorithm Based on Magic Square and a Novel Chaotic System for Image Encryption (1).pdf:PDF},
}

[JofielB]

Hello, I would like to work on this issue

[cboyce376]

A group of us from Adelaide University are going to work on this issue over the next 4 weeks.

[Pikayue11]

Hi, I think it has already been 4 weeks and I am interested in this issue. Could I try to fix it?