Feature: Add --probSpecsDir option

The user can now tell the program to use an existing
`problem-specifications` directory, in which case the program does a
`fetch` rather than making a temporary shallow clone.

This is one of the biggest possible speed optimisations, given that the
program running time in non-interactive mode is limited by the time
taken to establish an up-to-date `problem-specifications`directory.
However, in the future we could add an `--offline` option (or similar).

This commit also makes it easier to add tests.

Decisions:
- Show an error if the given `problem-specifications` working directory
  is not clean, rather than asking the user or stashing changes.
- Try to be strict about the user's `problem-specifications` directory,
  and do not silently `checkout` or `merge`, at least for now.
- Don't assume the user has a remote named 'upstream'.
- Allow the given `problem-specifications` repo to be a shallow clone:
  don't check that it's actually a `problem-specifications` repo by
  requiring it to contain some specified SHA-1.

Closes: exercism#47

src/cli.nim

@@ -16,9 +16,11 @@ type
     exercise*: Option[string]
     mode*: Mode
     verbosity*: Verbosity
+    probSpecsDir*: Option[string]
 
   Opt = enum
-    optExercise, optCheck, optMode, optVerbosity, optHelp, optVersion
+    optExercise, optCheck, optMode, optVerbosity, optProbSpecsDir,
+    optHelp, optVersion
 
   OptKey = tuple
     short: string
@@ -32,6 +34,7 @@ const
     ("c", "check"),
     ("m", "mode"),
     ("o", "verbosity"),
+    ("p", "probSpecsDir"),
     ("h", "help"),
     ("v", "version"),
   ]
@@ -54,6 +57,7 @@ Options:
   -{optCheck.short}, --{optCheck.long}                  Check if there are missing tests. Doesn't update the tests. Terminates with a non-zero exit code if one or more tests are missing
   -{optMode.short}, --{optMode.long} <mode>            What to do with missing test cases. Allowed values: c[hoose], i[nclude], e[xclude]
   -{optVerbosity.short}, --{optVerbosity.long} <verbosity>  The verbosity of output. Allowed values: q[uiet], n[ormal], d[etailed]
+  -{optProbSpecsDir.short}, --{optProbSpecsDir.long} <dir>     Use this `problem-specifications` directory, rather than cloning temporarily
   -{optHelp.short}, --{optHelp.long}                   Show this help message and exit
   -{optVersion.short}, --{optVersion.long}                Show this tool's version information and exit"""
 
@@ -63,7 +67,7 @@ proc showVersion =
   echo &"Canonical Data Syncer v{NimblePkgVersion}"
   quit(0)
 
-proc showError(s: string) =
+proc showError*(s: string) =
   stdout.styledWrite(fgRed, "Error: ")
   stdout.write(s)
   stdout.write("\n\n")
@@ -134,6 +138,9 @@ proc processCmdLine*: Conf =
       of optVerbosity.short, optVerbosity.long:
         showErrorForMissingVal(kind, key, val)
         result.verbosity = parseVerbosity(kind, key, val)
+      of optProbSpecsDir.short, optProbSpecsDir.long:
+        showErrorForMissingVal(kind, key, val)
+        result.probSpecsDir = some(val)
       of optHelp.short, optHelp.long:
         showHelp()
       of optVersion.short, optVersion.long:

src/probspecs.nim

@@ -1,4 +1,4 @@
-import std/[json, options, os, osproc, sequtils, strformat, strutils]
+import std/[json, options, os, osproc, sequtils, strformat, strscans, strutils]
 import cli, logger
 
 type
@@ -102,12 +102,88 @@ proc findProbSpecsExercises(repo: ProbSpecsRepo, conf: Conf): seq[ProbSpecsExerc
     if conf.exercise.isNone or conf.exercise.get() == repoExercise.slug:
       result.add(initProbSpecsExercise(repoExercise))
 
-proc findProbSpecsExercises*(conf: Conf): seq[ProbSpecsExercise] =
-  let probSpecsRepo = initProbSpecsRepo()
-
+template withDir(dir: string; body: untyped): untyped =
+  ## Changes the current directory to `dir` temporarily.
+  let startDir = getCurrentDir()
   try:
-    probSpecsRepo.remove()
-    probSpecsRepo.clone()
-    probSpecsRepo.findProbSpecsExercises(conf)
+    setCurrentDir(dir)
+    body
   finally:
-    probSpecsRepo.remove()
+    setCurrentDir(startDir)
+
+proc getNameOfRemote(probSpecsDir, location: string): string =
+  ## Returns the name of the remote in `probSpecsDir` that points to `location`.
+  ##
+  ## Raises an error if there is no remote that points to `location`.
+  # There's probably a better way to do this than parsing `git remote -v`.
+  let (remotes, errRemotes) = execCmdEx("git remote -v")
+  if errRemotes != 0:
+    showError("could not run `git remote -v` in the given " &
+              &"problem-specifications directory: '{probSpecsDir}'")
+  var remoteName, remoteUrl: string
+  for line in remotes.splitLines():
+    discard line.scanf("$s$w$s$+fetch)$.", remoteName, remoteUrl)
+    if remoteUrl.contains(location):
+      return remoteName
+  showError(&"there is no remote that points to '{location}' in the " &
+            &"given problem-specifications directory: '{probSpecsDir}'")
+
+proc validateProbSpecsRepo(probSpecsRepo: ProbSpecsRepo) =
+  ## Raises an error if the given `probSpecsRepo` is not a valid
+  ## `problem-specifications` repo that is up-to-date with upstream.
+  const mainBranchName = "master"
+
+  let probSpecsDir = probSpecsRepo.dir
+  logDetailed(&"Using user-provided problem-specifications dir: {probSpecsDir}")
+
+  # Exit if the given directory does not exist.
+  if not dirExists(probSpecsDir):
+    showError("the given problem-specifications directory does not exist: " &
+              &"'{probSpecsDir}'")
+
+  withDir probSpecsDir:
+    # Exit if the given directory is not a git repo.
+    if execCmd("git rev-parse") != 0:
+      showError("the given problem-specifications directory is not a git " &
+                &"repository: '{probSpecsDir}'")
+
+    # Exit if the working directory is not clean.
+    if execCmd("git diff-index --quiet HEAD") != 0: # Ignores untracked files.
+      echo &"\nUnstaged changes in {probSpecsDir}:"
+      discard execCmd("git status --short --untracked=no")
+      showError("the given problem-specifications working directory is not " &
+                &"clean: '{probSpecsDir}'")
+
+    # Find the name of the remote that points to upstream. Don't assume the
+    # remote is called 'upstream'.
+    # Exit if the repo has no remote that points to upstream.
+    const upstreamLocation = "github.com/exercism/problem-specifications"
+    let remoteName = getNameOfRemote(probSpecsDir, upstreamLocation)
+
+    # For now, just exit with an error if the HEAD is not up-to-date with
+    # upstream, even if it's possible to do a fast-forward merge.
+    if execCmd(&"git fetch --quiet {remoteName} {mainBranchName}") != 0:
+      showError(&"failed to fetch `{mainBranchName}` in " &
+                &"problem-specifications directory: '{probSpecsDir}'")
+
+    # Allow HEAD to be on a non-`master` branch, as long as it's up-to-date
+    # with `upstream/master`.
+    let (revHead, _) = execCmdEx("git rev-parse HEAD")
+    let (revUpstream, _) = execCmdEx(&"git rev-parse {remoteName}/{mainBranchName}")
+    if revHead != revUpstream:
+      showError("the given problem-specifications directory is not " &
+                &"up-to-date: '{probSpecsDir}'")
+
+proc findProbSpecsExercises*(conf: Conf): seq[ProbSpecsExercise] =
+  if conf.probSpecsDir.isSome():
+    let probSpecsRepo = ProbSpecsRepo(dir: conf.probSpecsDir.get())
+    validateProbSpecsRepo(probSpecsRepo)
+    result = probSpecsRepo.findProbSpecsExercises(conf)
+  else:
+    let probSpecsRepo = initProbSpecsRepo()
+    try:
+      probSpecsRepo.remove()
+      probSpecsRepo.clone()
+      result = probSpecsRepo.findProbSpecsExercises(conf)
+    finally:
+      probSpecsRepo.remove()