Feature: Add --trackDir option

With this commit, we can now establish a beginning state by specifying:
- a track directory
- a problem-specifications directory
- the offline mode

This allows us to do black-box testing of the release binary, running
something like:
    canonical_data_syncer -t /tmp/python -p /tmp/my_prob_specs --offline
and then asserting that the changes made are as expected.

Closes: exercism#50

README.md

@@ -16,6 +16,7 @@ Options:
   -v, --verbosity <verbosity>  The verbosity of output. Allowed values: q[uiet], n[ormal], d[etailed]
   -p, --prob-specs-dir <dir>   Use this `problem-specifications` directory, rather than cloning temporarily
   -o, --offline                Do not check that the directory specified by `-p, --prob-specs-dir` is up-to-date
+  -t, --track-dir <dir>        Specify a track directory to use instead of the current directory
   -h, --help                   Show this help message and exit
       --version                Show this tool's version information and exit
 ```

src/cli.nim

@@ -19,6 +19,7 @@ type
     verbosity*: Verbosity
     probSpecsDir*: string
     offline*: bool
+    trackDir*: string
 
   Opt = enum
     optExercise = "exercise"
@@ -27,6 +28,7 @@ type
     optVerbosity = "verbosity"
     optProbSpecsDir = "probSpecsDir"
     optOffline = "offline"
+    optTrackDir = "trackDir"
     optHelp = "help"
     optVersion = "version"
 
@@ -95,6 +97,7 @@ Options:
   {list(optVerbosity)} <verbosity>  The verbosity of output. {allowedValues(Verbosity)}
   {list(optProbSpecsDir)} <dir>   Use this `problem-specifications` directory, rather than cloning temporarily
   {list(optOffline)}                Do not check that the directory specified by `{list(optProbSpecsDir)}` is up-to-date
+  {list(optTrackDir)} <dir>        Specify a track directory to use instead of the current directory
   {list(optHelp)}                   Show this help message and exit
   {list(optVersion)}                Show this tool's version information and exit"""
 
@@ -124,6 +127,7 @@ proc initConf: Conf =
     verbosity: verNormal,
     probSpecsDir: "",
     offline: false,
+    trackDir: "",
   )
 
 func normalizeOption(s: string): string =
@@ -196,6 +200,8 @@ proc processCmdLine*: Conf =
         result.probSpecsDir = val
       of optOffline:
         result.offline = true
+      of optTrackDir:
+        result.trackDir = val
       of optHelp:
         showHelp()
       of optVersion:

src/tracks.nim

@@ -83,5 +83,9 @@ proc findTrackExercises(repo: TrackRepo, conf: Conf): seq[TrackExercise] =
       result.add(newTrackExercise(repoExercise))
 
 proc findTrackExercises*(conf: Conf): seq[TrackExercise] =
-  let trackRepo = newTrackRepo()
+  let trackRepo =
+    if conf.trackDir.len > 0:
+      TrackRepo(dir: conf.trackDir)
+    else:
+      newTrackRepo()
   trackRepo.findTrackExercises(conf)