amari.xlog: Fix parsing of logspec options

Fix off-by-one error in `amari.xlog.LogSpec.parse` which truncated the last
character of options, e.g. `stats[rf]/60s` would parse option `r` instead of `rf`.

/reviewed-by @kirr
/reviewed-on kirr/xlte!1

amari/xlog.py

@@ -108,7 +108,7 @@ class LogSpec:
             _ = tail.find(']')
             if _ == -1:
                 bad("missing closing ]")
-            optv = tail[1:_-1].split(',')
+            optv = tail[1:_].split(',')
             tail = tail[_+1:]
 
         for c in '[]/ ':

amari/xlog_test.py

@@ -78,3 +78,12 @@ zzzqqqrrrr
     # EOF
     _ = xr.read()
     assert _ is None
+
+
+def test_LogSpec():
+    logspec = "stats[samples,rf]/60s"
+    spec = xlog.LogSpec.parse(logspec)
+
+    assert spec.query == "stats"
+    assert spec.optv == ["samples", "rf"]
+    assert spec.period == 60.0