Add fetch tests

  - adds `fetch` tests for the following scenarios:
    * empty deps
    * empty dir
    * mutually recursive
    * self referential

corral/cmd/_test.pony

@@ -9,3 +9,4 @@ actor Main is TestList
 
   fun tag tests(test: PonyTest) =>
    _TestCmdUpdate.make().tests(test)
+   _TestCmdFetch.make().tests(test)

corral/cmd/_test_cmd_fetch.pony

@@ -0,0 +1,102 @@
+use "files"
+use "ponytest"
+use "../bundle"
+use "../util"
+use "../vcs"
+
+actor _TestCmdFetch is TestList
+  new make() =>
+    None
+
+  fun tag tests(test: PonyTest) =>
+    test(_TestFetchEmptyDeps)
+    test(_TestFetchEmptyFile)
+    test(_TestFetchMutuallyRecursive)
+    test(_TestFetchSelfReferential)
+
+class iso _TestFetchEmptyDeps is UnitTest
+  """
+  Verify that when using corral.json with empty deps, that there
+  are never any sync, tag query, or checkout operations executed.
+  """
+
+  fun name(): String =>
+    "cmd/fetch/" + __loc.type_name()
+
+  fun apply(h: TestHelper) ? =>
+    _OpsRecorderFetchTestRunner(
+      h,
+      "empty-deps",
+      _OpsRecorder(h, 0, 0, 0))?
+
+class iso _TestFetchEmptyFile is UnitTest
+  """
+  Verify that when using corral.json with an empty deps file, that there
+  are never any sync, tag query, or checkout operations executed.
+  """
+
+  fun name(): String =>
+    "cmd/fetch/" + __loc.type_name()
+
+  fun apply(h: TestHelper) ? =>
+    _OpsRecorderFetchTestRunner(
+      h,
+      "empty-file",
+      _OpsRecorder(h, 0, 0, 0))?
+
+class iso _TestFetchSelfReferential is UnitTest
+  """
+  Verify that a self reference in a corral.json results in only 1 operation
+  """
+  fun name(): String =>
+    "cmd/fetch/" + __loc.type_name()
+
+  fun apply(h: TestHelper) ? =>
+    _OpsRecorderFetchTestRunner(
+      h,
+      "self-referential",
+      _OpsRecorder(h, 1, 0, 1))?
+
+class iso _TestFetchMutuallyRecursive is UnitTest
+  """
+  Verify that when using mutually recursive corral.json files that we
+  execute the correct number of operations
+  """
+
+  fun name(): String =>
+    "cmd/fetch/" + __loc.type_name()
+
+  fun apply(h: TestHelper) ? =>
+    _OpsRecorderFetchTestRunner(
+      h,
+      "mutually-recursive/foo",
+      _OpsRecorder(h, 2, 0, 2))?
+
+primitive _OpsRecorderFetchTestRunner
+  fun apply(h: TestHelper, dep_path: String val, recorder: _OpsRecorder) ? =>
+    """
+    Runs an _OpsRecorder test.
+    """
+    let auth = h.env.root as AmbientAuth
+    let log = Log(LvlNone, h.env.err, SimpleLogFormatter)
+    let fp: FilePath = _TestData.file_path_from(h, dep_path)?
+    let repo_cache = _TestRepoCache(auth, "_test_cmd_fetch_repo_cache")?
+    let ctx = Context(h.env, log, log, false, repo_cache)
+    let project = Project(auth, log, fp)
+    let bundle = Bundle.load(fp, log)?
+    let vcs_builder: VCSBuilder = _TestCmdFetchVCSBuilder(recorder)
+
+    let fetcher = _Fetcher(ctx, project, consume bundle, vcs_builder, 
+      recorder)
+
+    // when fetcher is finished, it will send a `cmd_completed` message to
+    // _OpsRecorder which will trigger pass/fail
+
+class val _TestCmdFetchVCSBuilder is VCSBuilder
+  let _recorder: _OpsRecorder
+
+  new val create(recorder: _OpsRecorder) =>
+    _recorder = recorder
+
+  fun val apply(kind: String): VCS =>
+    _RecordedVCS(_recorder)

corral/cmd/cmd_fetch.pony

@@ -18,7 +18,7 @@ class CmdFetch is CmdType
 
     match project.load_bundle()
     | let base_bundle: Bundle iso =>
-      _Fetcher(ctx, project, consume base_bundle, vcs_builder)
+      _Fetcher(ctx, project, consume base_bundle, vcs_builder, result_receiver)
     | let err: Error =>
       ctx.uout.err(err.message)
       ctx.env.exitcode(1)
@@ -31,16 +31,19 @@ actor _Fetcher
   let fetched: Set[Locator] = fetched.create()
 
   let _vcs_builder: VCSBuilder
+  let _results_receiver: CmdResultReceiver
 
   new create(ctx': Context,
     project': Project,
     base_bundle': Bundle iso,
-    vcs_builder: VCSBuilder)
+    vcs_builder: VCSBuilder,
+    results_receiver: CmdResultReceiver)
   =>
     ctx = ctx'
     project = project'
     base_bundle = consume base_bundle'
      _vcs_builder = vcs_builder
+     _results_receiver = results_receiver
     ctx.log.info("Fetching direct deps of project bundle: " + base_bundle.name())
     fetch_bundle_deps(base_bundle)
 
@@ -58,6 +61,7 @@ actor _Fetcher
         ctx.uout.info("fetch: would have fetched dep: " + dep.name() + " @ " + dep.version())
       end
     end
+    _results_receiver.cmd_completed()
 
   fun fetch_dep(dep: Dep val) =>
     try