mousepad editor warns "the document has been externally modified" when modifying a soft linked text file

[bobbaer]

1. RELEASE (XUBUNTU)
# lsb_release -rd
Description: Ubuntu 21.04
Release: 21.04

2. PACKAGE
# apt-cache policy mousepad
mousepad:
  Installed: 0.5.3-0ubuntu1
  Candidate: 0.5.3-0ubuntu1
  Version table:
 *** 0.5.3-0ubuntu1 500
        500 http://de.archive.ubuntu.com/ubuntu hirsute/universe amd64 Packages
        100 /var/lib/dpkg/status

3./4. DESCRIPTION
When opening a file with mousepad 0.5.3 in xubuntu 21.04 after doing changes to the file and hitting Ctrl+S to save the changes, a warning pops up with the following warning:
"Externally modified
The document has been externally modified. Do you want to continue saving?
If you save the document, all of the external changes will be lost"

Opening instead the file directly (i.e. not via soft link), mousepad will not issue the warning.

How to reproduce:
1. echo test > bla.txt
2. mousepad bla.txt
3. Do some changes and hit Ctrl+S -> this will save w/o dialog.
4. Quit mousepad with Ctrl+q
5. ln -s bla.txt blaln.txt
6. mousepad blaln.txt
7. Do some changes and hit Ctrl+S -> this will cause the dialog to open.

This behavious has changed from
  groovy 20.10 with mousepad 0.4.2-1 to
  hirsute 21.04 with mousepad 0.5.3-0ubuntu1.
An upgrade was made from groovy -> hirsute but this should also occur when running from live cd.

I also tried the newer and older binaries of mousepad from
  https://packages.ubuntu.com/impish/mousepad 0.5.4-0ubuntu1
  https://packages.ubuntu.com/groovy/mousepad 0.4.2-1
(just did a "dpkg -x *.deb ." and started the mousepad binary).

Impish's mousepad showed the same error.
Groovy's mousepad was working as before/expected.

I went quickly through the release notes of mousepad but could not find or see something related
https://gitlab.xfce.org/apps/mousepad/-/tags

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Kanehekili (jentiger-moratai)]

This happens also if the text file resides on a cifs mount. How to reproduce:
Create a textfile on cifs/smb mount
Open it with mousepad. Change something. The error message pops up when trying to save the document

[bobbaer (bobbaer)]

https://gitlab.xfce.org/apps/mousepad/-/issues/135
"Externally Modified" warning when saving file opened from symlink

[bobbaer (bobbaer)]

Working again in 21.10 impish.
Did not test cifs/smb.
But since 21.04 hirsute will be EOL I think we should close this bug.