1 files changed, 31 insertions, 1 deletions

diff --git a/src/config/mod.rs b/src/config/mod.rs
index 0aaccd6..b8a2ba0 100644
--- a/src/config/mod.rs
+++ b/src/config/mod.rs
@@ -122,7 +122,7 @@ pub(crate) const OPTIONS: &[OptionSpec] = &[
         Kind::List,
         "NAME,[NAME...]",
         None,
-        "Override checks that otherwise refuse to start: true for all, or names: swarmId (a document to start on is of another swarm than the state file remembers), badDocumentFile (an unusable document file: moved aside, start without it), replaceDocumentFile (recover-from while the document file holds a document).",
+        "Override checks that otherwise refuse to start (command line only: it is for one start): true for all, or names: swarmId (a document to start on is of another swarm than the state file remembers), badDocumentFile (an unusable document file: moved aside, start without it), replaceDocumentFile (recover-from while the document file holds a document).",
     ),
     option(
         "recover-from",
@@ -902,6 +902,16 @@ pub(crate) fn load() -> Result<Loaded> {
 }
 
 fn resolve(merged: Layer, files: Vec<PathBuf>) -> Result<Loaded> {
+    // An override is for the start it was given for; in a file it would silently apply
+    // to every start, e.g. replacing the document file with a backup each time.
+    if let Some(entry) = merged.get("force").filter(|entry| {
+        !entry.value.is_null() && matches!(entry.origin.provenance, Provenance::File(_))
+    }) {
+        bail!(
+            "force can only be given on the command line: it overrides checks for one start, and in a file ({}) it would apply to every start",
+            entry.origin
+        );
+    }
     // Unset options take their defaults.
     let object: serde_json::Map<String, JsonValue> = merged
         .iter()
@@ -958,6 +968,26 @@ mod tests {
     }
 
     #[test]
+    fn force_only_on_the_command_line() {
+        let from = |provenance| Entry {
+            value: json!(["swarmId"]),
+            origin: Origin {
+                provenance,
+                unset: false,
+                imports: Vec::new(),
+            },
+        };
+        let mut merged = layer(json!({ "htpasswd": "u" }));
+        merged.insert(
+            "force".to_owned(),
+            from(Provenance::File(PathBuf::from("continuum.toml"))),
+        );
+        assert!(resolve(merged.clone(), Vec::new()).is_err());
+        merged.insert("force".to_owned(), from(Provenance::Argument));
+        assert!(resolve(merged, Vec::new()).is_ok());
+    }
+
+    #[test]
     fn options_and_settings_agree() {
         // Every option is a Settings field, and every field an option.
         let loaded = resolve(layer(json!({ "htpasswd": "users" })), Vec::new()).unwrap();