Use standardized data directories on linux - #2648

If you agree to adding a new dependency, I would add Xdg.Directories like #2088 to simplify handling of the standard paths. Basically GetXdgDir() and its clunky string based handling could go away. I wanted to use enums, but as I found C# does not spport custom properties on enum variants, only in a very clunky way with reflection.

I've pushed my implementation for this feature.

There's only one thing left: I keep to store the process.lock (used for singleton mode) in ${XDG_CACHE_HOME}/SourceGit/process.lock instead of ${XDG_RUNTIME_HOME}/SourceGit/process.lock. This is because some Linux distro has strict limitations for file in ${XDG_RUNTIME_HOME}:

• File modes
• May be auto cleaned by the OS
• Must be updated per 6 hours
• ...

Are you sure XDG_RUNTIME_HOME is automatically cleaned by some distro?

In fact, I would expect XDG_CACHE_HOME to be cleaned up periodically. The former is just a tmpfs, everything there is automatically lost on system shutdown. Can I ask which distro have you seen to be running cleanups on XDG_RUNTIME_HOME?

Edit: oh, indeed

Files in this directory MAY be subjected to periodic clean-up. To ensure that your files are not removed, they should have their access time timestamp modified at least once every 6 hours of monotonic time or the 'sticky' bit should be set on the file.
-- https://specifications.freedesktop.org/basedir/latest/#variables

I believe the speciifc file mode of 700 only applies to the runtime directory itself:

The directory MUST be owned by the user, and they MUST be the only one having read and write access to it. Its Unix access mode MUST be 0700.

On my system I have files with all kinds of permission modes set in there, even from modern, generally well behaved software like pipewire, dbus and systemd.

The auto cleanup needs to be taken care of, thats right. It kind of makes sense to auto delete unused files, to avoid getting the memory filled up over time, but I think the cleanup routines could at least check additionally whether the file is opened in any process. Because if it is, deletion wont reclaim any space anyway.

SourceGit would be using the XDG_RUNTIME_HOME directory very lightly, just a single file and that too always on the same path, so I think it would be okay if you just set the sticky bit on it. But it would still be good to delete the lock file on exit and crashes.

I think this is how its done in dotnet: https://learn.microsoft.com/en-us/dotnet/api/system.io.file.setunixfilemode?view=net-10.0

using System;
using System.IO;

string filePath = "/path/to/file";
File.SetUnixFileMode(filePath, File.GetUnixFileMode(filePath) | UnixFileMode.StickyByte);

Done.

• On Windows
  • Portable mode: it stores in data/process.lock
  • Non-portable mode: it stores in %APPDATA%/SourceGit/process.lock
• On macOS, it stores in ~/Library/Application Support/SourceGit/process.lock
• On Linux
  • Portable mode: it stores in data/process.lock
  • Non-portable mode: it stores in $XDG_RUNTIME_DIR/sourcegit.instance.lock

You can download the latest CI build from GitHub Action.