lib/config: Add file inside folder marker directory

[calmh]

Purpose

Avoid the issue where the folder marker is deleted by overzealous cleanup tools because it's just a useless, empty directory.

We create a small file containing a an admonishment to not delete the directory, and some metadata that is just for human consumption at the moment. (But it would parse as a valid yaml file if we wanted to read this, at some point.)

This will only apply when creating a folder marker, that is, existing setups will not gain the file automatically. Obviously, when using a custom folder marker none of this applies.

Testing

I've created and deleted a few folders and it appears to behave as I expect.

Screenshots

jb@ok:~/somefolder % ls -la
total 0
drwxr-xr-x   3 jb  staff   96 May  1 08:52 ./
drwx------  12 jb  staff  384 May  1 08:52 ../
drwxr-xr-x   3 jb  staff   96 May  1 08:52 .stfolder/
jb@ok:~/somefolder % ls -l .stfolder
total 8
-rw-r--r--  1 jb  staff  122 May  1 08:52 syncthing-folder-39a4b0.txt
jb@ok:~/somefolder % cat .stfolder/syncthing-folder-39a4b0.txt
# This directory is a Syncthing folder marker.
# Do not delete.

folderID: xtdca-cudyf
created: 2024-05-01T08:52:49+02:00

[acolomb]

Looks good code-wise. Just a few questions.

I could see more checks being done when finding the marker (e.g. checking whether the folder ID matches, maybe even record and check the device ID?). But it's absolutely OK to skip that in this first step.

[acolomb]

Also folderLabel, or do you think this info is too fragile (not guaranteed to be immutable)?

[calmh]

Yeah that, it can change and this file won't.

[acolomb]

If this is no longer needed, it should be noted in the commit message. I suspect it stems from the time we transitioned from a marker file to a marker directory?

Isn't the same logic needed for the content file then?

[calmh]

It's based on a misunderstanding to begin with. The only thing these bits do on Windows is set the read only flag, which we don't do here. Having the defaults remove group & other write bits on unixes is best practice. I'll make a note of it.