[FR] Reuse existing window/instance when opening files in file manager

[N46AN]

OS: Debian 9
ReText: 6.0.2

Step to reproduce:

1. Open a file with ReText;
2. In the OS/DE filemanager, such as nautilus/dolphin/thunar, open another file with ReText.

Actual behaviour:
Step 2 creates a new window and instance of ReText.

Expected behaviour:
Step 2 should reuse the existing window and instance created in step 1.

[mitya57]

This is a duplicate of #148. It will be non-trivial to implement, and pull requests are welcome.

[mitya57]

This is now fixed in master branch (see #476). Any feedback is appreciated.