Support XDG Base Directory

[kevinschoon]

Pomo should support the XDG Base Directory specification and not default to polluting the home directory with ~/.pomo.

[strogiyotec]

Is it ok to support it using environmental variables in order to keep backward compatibility ?
As an example, postgres keeps history file in home directory and in order to change this behavior one should add this to .bashrc or .zshrc

export PSQL_HISTORY="$XDG_DATA_HOME/psql/history"

So in case of pomo it would be

export POMO_CONFIG="$XDG_CONFIG_HOME/pomo/pomo.json"
export POMO_DB="$XDG_DATA_HOME/pomo/pomo.db"

[kevinschoon]

Currently the default configuration for pomo looks like this:

{
  "colors": null,
  "dateTimeFmt": "2006-01-02 15:04",
  "basePath": "/home/kevin/.pomo",
  "dbPath": "/home/kevin/.pomo/pomo.db",
  "socketPath": "/home/kevin/.pomo/pomo.sock",
  "iconPath": "/home/kevin/.pomo/icon.png"
}

Where basePath includes the sqlite database, configuration, runtime socket, and supplemental files.
On Linux per the XDG spec, we should actually store the configuration with a structure like this:

# configuration is stored in
~/.config/pomo/config.json
# the database and supplemental files are in a shared directory
~/.local/share/pomo/pomo.db
~/.local/share/pomo/icon.png
# the runtime socket is stored in path like
/run/user/1000/pomo.socket

Regarding backward compatibility I'm fine with just adding some documentation instructing users to move their sqlite file into the new default path.

There is some relevant discussion in golang/go#29960 but I'm not entirely sure what the right solution is for non-linux systems.
Below is some example code that returns the correct default paths on Linux.

package main

import (
	"fmt"
	"os"
	"os/user"
	"path"
)

func getConfigPath() string {
	basepath, err := os.UserConfigDir()
	if err != nil {
		panic(err)
	}
	return path.Join(basepath, ".pomo/config.json")
}

func getDataDir() string {
	basepath := os.Getenv("XDG_DATA_HOME")
	if basepath == "" {
		user, _ := user.Current()
		return path.Join(user.HomeDir, ".local/share/pomo")
	}
	return path.Join(basepath, "pomo")
}

func getSocketPath() string {
	basepath := os.Getenv("XDG_RUNTIME_DIR")
	if basepath == "" {
		user, _ := user.Current()
		// BUG: What to do on OSX/Windows?
		return path.Join("/run/user", user.Uid, "pomo.socket")
	}
	return path.Join(basepath, "pomo.socket")
}

func main() {
	fmt.Println(getConfigPath())
	fmt.Println(getDataDir())
	fmt.Println(getSocketPath())
}

/home/kevin/.config/.pomo/config.json
/home/kevin/.local/share/pomo
/run/user/1000/pomo.socket

[kevinschoon]

Implemented with #58