Support add_snapshots on cli

.changelogs/2021-10-11-issue23-client.md

@@ -0,0 +1,2 @@
+- The `avoid_snapshots` configuration value, if set, will cause the replica to
+  avoid creating snapshots unless required.

cli/src/invocation/cmd/sync.rs

@@ -1,13 +1,14 @@
+use crate::settings::Settings;
 use taskchampion::{server::Server, Replica};
 use termcolor::WriteColor;
 
 pub(crate) fn execute<W: WriteColor>(
     w: &mut W,
     replica: &mut Replica,
+    settings: &Settings,
     server: &mut Box<dyn Server>,
 ) -> Result<(), crate::Error> {
-    // TODO: configurable avoid_snapshots
-    replica.sync(server, false)?;
+    replica.sync(server, settings.avoid_snapshots)?;
     writeln!(w, "sync complete.")?;
     Ok(())
 }
@@ -25,9 +26,10 @@ mod test {
         let mut replica = test_replica();
         let server_dir = TempDir::new().unwrap();
         let mut server = test_server(&server_dir);
+        let settings = Settings::default();
 
         // Note that the details of the actual sync are tested thoroughly in the taskchampion crate
-        execute(&mut w, &mut replica, &mut server).unwrap();
+        execute(&mut w, &mut replica, &settings, &mut server).unwrap();
         assert_eq!(&w.into_string(), "sync complete.\n")
     }
 }

cli/src/invocation/mod.rs

@@ -87,7 +87,7 @@ pub(crate) fn invoke(command: Command, settings: Settings) -> Result<(), crate::
             ..
         } => {
             let mut server = get_server(&settings)?;
-            return cmd::sync::execute(&mut w, &mut replica, &mut server);
+            return cmd::sync::execute(&mut w, &mut replica, &settings, &mut server);
         }
 
         // handled in the first match, but here to ensure this match is exhaustive

cli/src/settings/settings.rs

@@ -22,6 +22,7 @@ pub(crate) struct Settings {
 
     /// replica
     pub(crate) data_dir: PathBuf,
+    pub(crate) avoid_snapshots: bool,
 
     /// remote sync server
     pub(crate) server_client_key: Option<String>,
@@ -91,6 +92,7 @@ impl Settings {
         let table_keys = [
             "data_dir",
             "modification_count_prompt",
+            "avoid_snapshots",
             "server_client_key",
             "server_origin",
             "encryption_secret",
@@ -124,6 +126,20 @@ impl Settings {
             Ok(())
         }
 
+        fn get_bool_cfg<F: FnOnce(bool)>(
+            table: &Table,
+            name: &'static str,
+            setter: F,
+        ) -> Result<()> {
+            if let Some(v) = table.get(name) {
+                setter(
+                    v.as_bool()
+                        .ok_or_else(|| anyhow!(".{}: not a boolean value", name))?,
+                );
+            }
+            Ok(())
+        }
+
         get_str_cfg(table, "data_dir", |v| {
             self.data_dir = v.into();
         })?;
@@ -132,6 +148,10 @@ impl Settings {
             self.modification_count_prompt = Some(v);
         })?;
 
+        get_bool_cfg(table, "avoid_snapshots", |v| {
+            self.avoid_snapshots = v;
+        })?;
+
         get_str_cfg(table, "server_client_key", |v| {
             self.server_client_key = Some(v);
         })?;
@@ -313,6 +333,7 @@ impl Default for Settings {
             filename: None,
             data_dir,
             modification_count_prompt: None,
+            avoid_snapshots: false,
             server_client_key: None,
             server_origin: None,
             encryption_secret: None,

docs/src/config-file.md

@@ -46,6 +46,12 @@ If using a remote server:
 * `server_client_key` -  Client key to identify this replica to the sync server (a UUID)
   If not set, then sync is done to a local server.
 
+## Snapshots
+
+* `avoid_snapshots` - If running on a CPU-, memory-, or bandwidth-constrained
+  device, set this to true.  The effect is that this replica will wait longer
+  to produce a snapshot, in the hopes that other replicas will do so first.
+
 ## Reports
 
 * `reports` - a mapping of each report's name to its definition.