~ tilde is not suppored in a global config

[thebino]

If I want to use ~ in any path in the global config, it will not parse the config and stop with a non-helpful error.

For example if I want to write a logfile to the local .config directory

log-file = "~/.config/rustic/rustic.log"

Same for sources

[[backup.sources]]
source = "~/foo"

On mac the error message is also kind of strange (without showing which config is used)

error: rustic-rs fatal error: I/O operation failed: No such file or directory (os error 2)

[aawsome]

As ~ is IMO just a special case of variable substitution (here the env variable $HOME), I'm closing this as duplicate of #942

[simonsan]

Discovered this library lately: https://docs.rs/crate/shellexpand/3.1.0

Maybe worth another discussion, if we can implement it with that more easily?

Reopening for that discussion

[simonsan]

Copying over the discussion points of env var expansion:

This feature is a bit more involved as there are more questions arising:

• Do we only want variable substitution in filenames or elsewhere in the config?
• Do we want to allow substition only within strings?
• Do we want to first parse the TOML, then substitute what is appropriate or first substitute and then parse (which would allow to define TOML structures within env variables)?

Originally posted by @aawsome in #942 (comment)