Allow building without self_update command

The self-update subcommand is undesirable if rustic is installed using
the system package manager.

Cargo.toml

@@ -31,9 +31,10 @@ description = { workspace = true }
 members = ["crates/rustic_testing", "xtask"]
 
 [features]
-default = []
+default = ["self-update"]
 mimalloc = ["dep:mimalloc"]
 jemallocator = ["dep:jemallocator-global"]
+self-update = ["dep:self_update", "dep:semver"]
 
 [[bin]]
 name = "rustic"
@@ -67,8 +68,8 @@ serde_with = { workspace = true }
 
 # other dependencies
 chrono = { workspace = true }
-self_update = { workspace = true }
-semver = { workspace = true }
+self_update = { workspace = true, optional = true }
+semver = { workspace = true, optional = true }
 
 # commands
 clap = { workspace = true }

src/commands.rs

@@ -18,6 +18,7 @@ pub(crate) mod prune;
 pub(crate) mod repair;
 pub(crate) mod repoinfo;
 pub(crate) mod restore;
+#[cfg(feature = "self-update")]
 pub(crate) mod self_update;
 pub(crate) mod show_config;
 pub(crate) mod snapshots;
@@ -33,8 +34,8 @@ use crate::{
         backup::BackupCmd, cat::CatCmd, check::CheckCmd, completions::CompletionsCmd,
         config::ConfigCmd, copy::CopyCmd, diff::DiffCmd, dump::DumpCmd, forget::ForgetCmd,
         init::InitCmd, key::KeyCmd, list::ListCmd, ls::LsCmd, merge::MergeCmd, prune::PruneCmd,
-        repair::RepairCmd, repoinfo::RepoInfoCmd, restore::RestoreCmd, self_update::SelfUpdateCmd,
-        show_config::ShowConfigCmd, snapshots::SnapshotCmd, tag::TagCmd,
+        repair::RepairCmd, repoinfo::RepoInfoCmd, restore::RestoreCmd, show_config::ShowConfigCmd,
+        snapshots::SnapshotCmd, tag::TagCmd,
     },
     config::{progress_options::ProgressOptions, RusticConfig},
     {Application, RUSTIC_APP},
@@ -108,7 +109,8 @@ enum RusticCmd {
     ShowConfig(ShowConfigCmd),
 
     /// Update to the latest rustic release
-    SelfUpdate(SelfUpdateCmd),
+    #[cfg(feature = "self-update")]
+    SelfUpdate(self_update::SelfUpdateCmd),
 
     /// Remove unused data or repack repository pack files
     Prune(PruneCmd),