Fix a long-fork checker

```
$ java -jar ~/sources/elle-cli/target/elle-cli-0.1.7-standalone.jar --verbose --model long-fork histories/jepsen/long-fork.edn
{"reads-count":2,
 "early-read-count":0,
 "late-read-count":0,
 "valid?":false,
 "forks":
 [[{"index":3,
    "time":-1,
    "type":"ok",
    "process":null,
    "f":"read",
    "value":[["r", 2, 1], ["r", 0, 1], ["r", 1, null]]},
   {"index":1,
    "time":-1,
    "type":"ok",
    "process":null,
    "f":"read",
    "value":[["r", 0, 1], ["r", 1, 1], ["r", 2, null]]}]]}
```

Fixes #43

CHANGELOG.md

@@ -13,6 +13,7 @@ change log follows the conventions of
 ### Fixed
 
 - A `set` checker (#44).
+- A `long-fork` checker (#43).
 
 ### Changed
 

histories/jepsen/long-fork.edn

@@ -0,0 +1,4 @@
+[{:type :invoke, :f :read, :value [[:r 0 nil] [:r 1 nil] [:r 2 nil]]},
+{:type :ok, :f :read, :value [[:r 0 1] [:r 1 1] [:r 2 nil]]},
+{:type :invoke, :f :read, :value [[:r 2 nil] [:r 0 nil] [:r 1 nil]]},
+{:type :ok, :f :read, :value [[:r 2 1]   [:r 0 1]   [:r 1 nil]]}]

src/elle_cli/cli.clj

@@ -138,7 +138,10 @@
     :parse-fn #(Integer/parseInt %)]
 
    ; Jepsen-specific options.
-   ; None.
+   ["-g" "--group-size GROUP-SIZE"
+    "(Jepsen) A group size."
+    :default 0
+    :parse-fn #(Integer/parseInt %)]
 
    ; Knossos-specific options.
    ; None.
@@ -184,7 +187,8 @@
        "bank" (jepsen-model/check-safe (checker-fn {:negative-balances? true}) nil history)
        "counter" (jepsen-model/check-safe (checker-fn) nil history)
        "set" (jepsen-model/check-safe (checker-fn) nil history)
-       "set-full" (jepsen-model/check-safe (checker-fn) nil history))))
+       "set-full" (jepsen-model/check-safe (checker-fn) nil history)
+       "long-fork" (jepsen-model/check-safe (checker-fn (get options :group-size)) nil history))))
 
 (defn read-fn-by-extension
   "Take a path to file and returns a function for reading that file."

test.sh

@@ -61,5 +61,6 @@ run_test 1 "--model bank histories/jepsen/bank.edn"
 run_test 1 "--model bank histories/jepsen/bank.json"
 run_test 1 "--model bank histories/jepsen/bank-tidb.edn"
 
+run_test 1 "--model long-fork --group-size 3 histories/jepsen/long-fork.edn"
 
 exit $suite_status