Make bisect playable and validate commit_in_future using Git author timestamps

LevelsCompare.md

@@ -58,7 +58,7 @@ This file records the upstream Ruby setup and validation intent beside the Andro
 | `squash` | Creates initial hidden commit plus README and three squash-target README updates. | Same commit sequence. | Equivalent. |
 | `merge_squash` | Creates master and `long-feature-branch` with multiple feature changes. | Native setup creates the same branch and `file3` feature effect. | Mostly equivalent; Android currently validates less detail. |
 | `reorder` | Creates commits `Initial Setup`, `First commit`, `Third commit`, `Second commit`. | Same order. | Equivalent. |
-| `bisect` | Copies upstream bisect fixture. | Initializes modeled bad hash `18ed2ac`. | Simplified setup; Android validates the intended answer directly. |
+| `bisect` | Copies upstream Ruby fixture where `ruby prog.rb 5` or `make test` identifies bad hash `18ed2ac`. | Creates a native Git history with `balance.txt`, `test-balance.sh`, and `known-good` tag. | Intentional Android adaptation: no Ruby or make dependency, but real `git bisect` remains playable. |
 | `stage_lines` | Commits initial `feature.rb`, then leaves two unstaged feature lines. | Initializes tracked `feature.rb` containing both feature lines. | Setup is close, but Android does not yet model partial staged vs unstaged hunks. |
 | `find_old_branch` | Copies fixture with recoverable `solve_world_hunger` branch. | Initializes branch map with `solve_world_hunger`. | Equivalent for visible exercise state. |
 | `revert` | Creates commits `First commit`, `Bad commit`, `Second commit`. | Same commit messages. | Equivalent. |
@@ -90,7 +90,7 @@ This file records the upstream Ruby setup and validation intent beside the Andro
 | `tag` | First tag is `new_tag`. | `new_tag` exists. | Equivalent. |
 | `push_tags` | Remote tag list contains `tag_to_be_pushed`. | `tag_to_be_pushed` is in `pushedTags`. | Equivalent state projection. |
 | `commit_amend` | One commit and amended commit contains two files. | One commit and `forgotten_file.rb` is tracked. | Equivalent. |
-| `commit_in_future` | Commit authored date is in the future. | Any commit exists. | Known gap: Android does not currently expose commit authored timestamps in `RepoState`. |
+| `commit_in_future` | Commit authored date is in the future. | At least one commit has an author timestamp later than the current system clock. | Equivalent. |
 | `reset` | `to_commit_second.rb` exists but is unstaged; `to_commit_first.rb` remains staged. | Same staged/unstaged split with one commit. | Equivalent. |
 | `reset_soft` | `newfile.rb` exists, is staged, and commit count is one. | Same. | Equivalent. |
 | `checkout_file` | `config.rb` no longer modified and commit count remains one. | `config.rb` content equals initial content. | Equivalent. |
@@ -119,7 +119,7 @@ This file records the upstream Ruby setup and validation intent beside the Andro
 | `squash` | Commit count is two. | Commit count at most two and "Adding README" remains. | Slightly stricter on preserving the base README commit. |
 | `merge_squash` | Commit count is three and all long-feature changes are included. | Squash action recorded and a commit exists. | Known gap: Android does not yet verify all squash file/content effects. |
 | `reorder` | `git log` subject order matches `Third.*Second.*First.*Initial`. | Modeled commit order becomes First, Second, Third. | Equivalent relative to Android's oldest-first commit list. |
-| `bisect` | Answer is hash prefix `18ed2ac`. | Answer is `18ed2ac`. | Equivalent. |
+| `bisect` | Answer is hash prefix `18ed2ac` after using Ruby/make fixture. | Learner can run `git bisect start HEAD known-good` and `git bisect run ./test-balance.sh`; Android accepts the discovered bad hash or the final bisect state. | Same lesson, different fixture to keep it playable without Ruby/make. |
 | `stage_lines` | Staged diff contains first feature line; unstaged diff contains second feature line. | `feature.rb` is staged. | Known gap: Android does not yet model partial hunk staging. |
 | `find_old_branch` | Current branch is `solve_world_hunger`. | Same. | Equivalent. |
 | `revert` | More than three commits and a revert of "Bad commit" exists. | A commit message starts with `Revert`. | Slightly looser; sufficient for current fixture. |
@@ -157,7 +157,6 @@ This file records the upstream Ruby setup and validation intent beside the Andro
 
 These are the remaining known non-parity items that need additional model support if exact upstream validation is required:
 
-- `commit_in_future`: add authored timestamp inspection to `CommitNode`/`RepoState`.
 - `stage_lines`: model partial staged vs unstaged hunks.
 - `merge_squash`: verify the exact squashed file/content effects.
 - `conflict`: model merge parent count or inspect merge commit parents.

README.md

@@ -126,7 +126,20 @@ The command engine has one app-facing runtime:
 
 The runtime exposes a `RepoState` surface to validators. In addition to files, commits, branches, tags, remotes, and config, the model tracks learning-relevant effects such as stashes, fetched remote refs, pushed branches/tags, submodules, and repository maintenance actions.
 
-Helper shell-like commands (`ls`, `pwd`, `cat`, `touch`, `mkdir`, `rm`, `echo`, `cd`) remain implemented in Kotlin so the mobile terminal behaves consistently across devices.
+Helper shell-like commands (`ls`, `pwd`, `cat`, `sh <script>`, `./<script>`, `touch`, `mkdir`, `rm`, `echo`, `cd`) remain implemented in Kotlin so the mobile terminal behaves consistently across devices.
+
+## Known Level Differences From Upstream
+
+The Android port keeps the upstream GitHug level order, but some upstream fixtures assume desktop tools, network access, Ruby, Perl/Python helpers, or direct filesystem behavior that should not be required in a mobile learning sandbox. Differences must be documented here when they are intentional.
+
+| Level | Upstream behavior | Android behavior | Why it differs |
+| --- | --- | --- | --- |
+| `bisect` | Copies the upstream Ruby fixture. The learner tests each checked-out commit with `ruby prog.rb 5` or `make test`, then answers the abbreviated hash `18ed2ac`. | Creates a native Git history with `balance.txt` and `test-balance.sh`. The learner can run `./test-balance.sh` or `sh test-balance.sh`, then use `git bisect start HEAD known-good` and `git bisect run ./test-balance.sh`. The level accepts the discovered bad commit hash or the final bisect state. | Android does not bundle Ruby or `make`. The replacement still demonstrates the real `git bisect` workflow: identify known good/bad endpoints, run a test at each checked-out commit, and find the first bad commit. |
+| `clone` / `clone_to_folder` | Clones `https://github.com/Gazler/cloneme` and checks the cloned repository content. | Accepts the intended clone command and models the resulting folder. | The app must remain playable offline and avoid relying on GitHub network access from a phone. |
+| `pull`, `fetch`, `push`, `push_branch`, `push_tags` | Use remote-style workflows from upstream fixtures. | Use local synthetic remotes created inside the sandbox and validate fetched/pushed refs through `RepoState`. | This preserves Git behavior without external network dependencies. |
+| `contribute` | Expects cloning upstream and finding a commit authored by the configured user. | Treated as a mobile/offline final prompt with a nonblank response. | The original workflow leaves the sandbox and depends on external contribution infrastructure. |
+| `stage_lines` | Requires partial hunk staging: one feature line staged and another left unstaged. | Currently validates that `feature.rb` is staged. | Android does not yet expose enough index-vs-working-tree hunk detail in `RepoState` to validate partial staging precisely. |
+| `rebase_onto`, `merge_squash`, `conflict`, `repack` | Upstream validates detailed object graph, file content, merge-parent, or object database details. | Android validates the relevant user-facing action or resulting state, but with less object-level detail in some cases. | The current `RepoState` projection does not expose every low-level Git object fact. These should be tightened when the state surface grows. |
 
 ## Level Authoring
 
@@ -138,6 +151,7 @@ When adding or changing a level:
 - Update `LevelsCompare.md` whenever level setup, validation, hints, or accepted solution behavior changes.
 - Prefer validators that inspect `RepoState` over validators that match command strings.
 - Add multiple `LevelTestCase` scenarios when more than one solution path should be accepted.
+- Update this README's known-differences table if the Android level intentionally differs from upstream Ruby GitHug.
 - Run `bash ./AndroidProjectTooling.sh --test` before building.
 
 ## Production Focus

app/build.gradle.kts

@@ -19,8 +19,8 @@ android {
         applicationId = "solutions.tretter.githugandroid"
         minSdk = 26
         targetSdk = 35
-        versionCode = 149
-        versionName = "0.1.148"
+        versionCode = 150
+        versionName = "0.1.149"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
         vectorDrawables.useSupportLibrary = true

app/src/main/java/solutions/tretter/githugandroid/GameModels.kt

@@ -17,6 +17,7 @@ data class GitFile(
 data class CommitNode(
     val id: String,
     val message: String,
+    val authorTimestampSeconds: Long? = null,
 )
 
 data class InteractiveAddSession(

app/src/main/java/solutions/tretter/githugandroid/GitRuntime.kt

@@ -148,18 +148,32 @@ class GitRepositoryRuntime private constructor(
             tokens
         } else {
             expandShellPathspecs(currentRepo, invocation.command)
-        }.normalizeGitStageAlias()
+        }
+            .normalizeGitStageAlias()
+            .normalizeGitBisectRunScriptShortcut()
 
         executeSyntheticGitCommand(currentRepo, command, expandedTokens, invocation.environment)?.let { return it }
 
         val result = when (expandedTokens.first()) {
             "git" -> currentRepo to runGit(nativeGit, workingDir, expandedTokens.drop(1), invocation.environment).outputLines
             "help", "?" -> currentRepo to commandReferenceLines()
-            else -> executeHelperCommand(sandboxRoot, workingDir, currentRepo, expandedTokens)
+            else -> executeExecutableShortcut(sandboxRoot, workingDir, currentRepo, expandedTokens)
+                ?: executeHelperCommand(sandboxRoot, workingDir, currentRepo, expandedTokens)
         }
 
         val inspectedRepo = inspectSandbox(level).copy(currentDir = result.first.currentDir)
-        return augmentObservedRepoFacts(currentRepo, inspectedRepo, expandedTokens) to result.second
+        return augmentObservedRepoFacts(currentRepo, inspectedRepo, expandedTokens, result.second) to result.second
+    }
+
+    private fun executeExecutableShortcut(
+        sandboxRoot: File,
+        workingDir: File,
+        currentRepo: RepoState,
+        tokens: List<String>,
+    ): Pair<RepoState, List<String>>? {
+        val executable = tokens.firstOrNull() ?: return null
+        if (!executable.startsWith("./") || executable.length <= 2) return null
+        return executeShellScript(sandboxRoot, workingDir, currentRepo, listOf("sh", executable) + tokens.drop(1))
     }
 
     fun completionCandidates(level: Level, currentRepo: RepoState, directoriesOnly: Boolean): List<String> {
@@ -190,7 +204,7 @@ class GitRepositoryRuntime private constructor(
             add("Native Git runtime:")
             add("  binary path: nativeLibraryDir/libgit.so")
             add("  selected ABI: ${Build.SUPPORTED_ABIS.firstOrNull() ?: "unknown"}")
-            add("  helper commands: ls/dir, pwd, cat, touch, mkdir/md, cd.., rm/del, echo")
+            add("  helper commands: ls/dir, pwd, cat, sh <script>, ./<script>, touch, mkdir/md, cd.., rm/del, echo")
             add("  visual editors: vi, vim, nano, emacs, ed, ex, edit, notepad")
             add("  git help <command>")
         }
@@ -366,6 +380,7 @@ class GitRepositoryRuntime private constructor(
                 if (!file.exists() || file.isDirectory) currentRepo to listOf("cat: $target: No such file")
                 else currentRepo to file.readLines().ifEmpty { listOf("") }
             }
+            "sh" -> executeShellScript(sandboxRoot, workingDir, currentRepo, tokens)
             "touch" -> {
                 val target = tokens.getOrNull(1) ?: return currentRepo to listOf("usage: touch <file>")
                 val file = File(workingDir, target)
@@ -418,6 +433,28 @@ class GitRepositoryRuntime private constructor(
         }
     }
 
+    private fun executeShellScript(
+        sandboxRoot: File,
+        workingDir: File,
+        currentRepo: RepoState,
+        tokens: List<String>,
+    ): Pair<RepoState, List<String>> {
+        val script = tokens.getOrNull(1) ?: return currentRepo to listOf("usage: sh <script>")
+        val scriptFile = File(workingDir, script).canonicalFile
+        if (!scriptFile.path.startsWith(sandboxRoot.path)) {
+            return currentRepo to listOf("sh: $script: Permission denied")
+        }
+        if (!scriptFile.isFile) {
+            return currentRepo to listOf("sh: $script: No such file")
+        }
+        val result = runShellProcess(
+            File(shellExecutable()),
+            workingDir,
+            tokens.drop(1),
+        )
+        return currentRepo to result.outputLines
+    }
+
     private fun placeholderManPage(topic: String): String {
         bundledManPage(topic)?.let { return it }
         val body = when (topic) {
@@ -645,7 +682,7 @@ class GitRepositoryRuntime private constructor(
             "revert", "stash" -> true
             "checkout" -> tokens.any { it == "file3" } || tokens.takeLast(2) == listOf("--", "config.rb")
             "submodule" -> tokens.getOrNull(2) == "add"
-            "commit" -> "merge-squash" in currentRepo.maintenanceActions || tokens.any { it == "--date" || it.startsWith("--date=") }
+            "commit" -> "merge-squash" in currentRepo.maintenanceActions
             else -> false
         }
         if (!shouldUseSandboxSemantics) return null
@@ -662,6 +699,20 @@ class GitRepositoryRuntime private constructor(
         }
     }
 
+    private fun List<String>.normalizeGitBisectRunScriptShortcut(): List<String> {
+        return if (
+            size >= 4 &&
+            this[0] == "git" &&
+            this[1] == "bisect" &&
+            this[2] == "run" &&
+            this[3].startsWith("./")
+        ) {
+            take(3) + listOf("sh") + drop(3)
+        } else {
+            this
+        }
+    }
+
     private fun executeEcho(workingDir: File, currentRepo: RepoState, tokens: List<String>): Pair<RepoState, List<String>> {
         val redirectIndex = tokens.indexOfFirst { it == ">" || it == ">>" }
         if (redirectIndex == -1 || redirectIndex == tokens.lastIndex) {
@@ -714,7 +765,7 @@ class GitRepositoryRuntime private constructor(
             }
         }
 
-        val logResult = runGit(nativeGit, sandbox, listOf("log", "--pretty=format:%h\t%s"))
+        val logResult = runGit(nativeGit, sandbox, listOf("log", "--pretty=format:%h\t%at\t%s"))
         val branchResult = runGit(nativeGit, sandbox, listOf("branch", "--list"))
         val remoteBranchResult = runGit(nativeGit, sandbox, listOf("branch", "-r", "--list"))
         val tagResult = runGit(nativeGit, sandbox, listOf("tag", "--list"))
@@ -742,8 +793,16 @@ class GitRepositoryRuntime private constructor(
         )
         val commits = if (logResult.exitCode == 0) {
             logResult.outputLines.filter { it.isNotBlank() }.mapNotNull { line ->
-                val parts = line.split('\t', limit = 2)
-                if (parts.isEmpty()) null else CommitNode(parts[0], parts.getOrElse(1) { "" })
+                val parts = line.split('\t', limit = 3)
+                if (parts.isEmpty()) {
+                    null
+                } else {
+                    CommitNode(
+                        id = parts[0],
+                        authorTimestampSeconds = parts.getOrNull(1)?.toLongOrNull(),
+                        message = parts.getOrElse(2) { "" },
+                    )
+                }
             }
         } else {
             emptyList()
@@ -828,10 +887,22 @@ class GitRepositoryRuntime private constructor(
         return listOf(tokens.first().value) + GitSandboxEngine.expandPathspecTokens(repo, tokens.drop(1))
     }
 
-    private fun augmentObservedRepoFacts(previousRepo: RepoState, inspectedRepo: RepoState, tokens: List<String>): RepoState {
+    private fun augmentObservedRepoFacts(
+        previousRepo: RepoState,
+        inspectedRepo: RepoState,
+        tokens: List<String>,
+        outputLines: List<String> = emptyList(),
+    ): RepoState {
         if (tokens.firstOrNull() != "git") return inspectedRepo
 
         return when (tokens.getOrNull(1)) {
+            "bisect" -> {
+                if (tokens.getOrNull(2) == "run" && outputLines.any { it.contains("is the first bad commit") }) {
+                    inspectedRepo.copy(maintenanceActions = previousRepo.maintenanceActions + inspectedRepo.maintenanceActions + "bisect-found")
+                } else {
+                    inspectedRepo.copy(maintenanceActions = previousRepo.maintenanceActions + inspectedRepo.maintenanceActions)
+                }
+            }
             "stash" -> inspectedRepo.copy(
                 stashes = mergeDistinct(previousRepo.stashes, inspectedRepo.stashes + "stash@{${previousRepo.stashes.size}}"),
             )
@@ -996,6 +1067,25 @@ class GitRepositoryRuntime private constructor(
         }
     }
 
+    private fun runShellProcess(binary: File, workingDir: File, arguments: List<String>): ProcessExecutionResult {
+        return try {
+            val process = ProcessBuilder(listOf(binary.absolutePath) + arguments)
+                .directory(workingDir)
+                .redirectErrorStream(true)
+                .apply {
+                    environment()["HOME"] = workingDir.absolutePath
+                    environment()["LC_ALL"] = "C"
+                }
+                .start()
+
+            val output = process.inputStream.bufferedReader().readLines()
+            val exit = process.waitFor()
+            ProcessExecutionResult(exitCode = exit, outputLines = output)
+        } catch (error: Exception) {
+            ProcessExecutionResult(exitCode = -1, outputLines = listOf("Shell execution failed: ${error.message ?: error::class.java.simpleName}"))
+        }
+    }
+
     private fun gitExecDirectory(binary: File): File {
         val directory = if (context != null) {
             File(context.filesDir, "git-exec")

app/src/main/java/solutions/tretter/githugandroid/RepoStateSaver.kt

@@ -8,7 +8,7 @@ val RepoStateSaver = listSaver<RepoState, Any>(
             state.initialized,
             state.headBranch,
             state.files.flatMap { listOf(it.name, it.content, it.staged.toString(), it.tracked.toString(), it.deleted.toString()) },
-            state.commits.flatMap { listOf(it.id, it.message) },
+            state.commits.flatMap { listOf(it.id, it.message, it.authorTimestampSeconds?.toString().orEmpty()) },
             state.branches.flatMap { listOf(it.key, it.value.toString()) },
             state.currentDir,
             state.tags,
@@ -53,9 +53,7 @@ val RepoStateSaver = listSaver<RepoState, Any>(
                     deleted = (it.getOrNull(4) as? String)?.toBoolean() ?: false,
                 )
             },
-            commits = commitParts.chunked(2).map {
-                CommitNode(it[0] as String, it[1] as String)
-            },
+            commits = commitParts.restoreCommitNodes(),
             branches = branchParts.chunked(2).associate { (it[0] as String) to (it[1] as String).toInt() },
             currentDir = saved[5] as String,
             tags = tags.filterIsInstance<String>(),
@@ -77,3 +75,21 @@ val RepoStateSaver = listSaver<RepoState, Any>(
         )
     }
 )
+
+private fun List<*>.restoreCommitNodes(): List<CommitNode> {
+    val hasTimestampColumn = size % 3 == 0 && chunked(3).all { chunk ->
+        val timestamp = chunk.getOrNull(2) as? String
+        timestamp.isNullOrEmpty() || timestamp.toLongOrNull()?.let { it >= 100_000_000L } == true
+    }
+    val width = if (hasTimestampColumn) 3 else 2
+
+    return chunked(width).mapNotNull { chunk ->
+        val id = chunk.getOrNull(0) as? String ?: return@mapNotNull null
+        val message = chunk.getOrNull(1) as? String ?: ""
+        CommitNode(
+            id = id,
+            message = message,
+            authorTimestampSeconds = if (hasTimestampColumn) (chunk.getOrNull(2) as? String)?.toLongOrNull() else null,
+        )
+    }
+}

app/src/main/java/solutions/tretter/githugandroid/levels/BisectLevel.kt

@@ -1,21 +1,89 @@
 package solutions.tretter.githugandroid
 
 /**
- * Port of the upstream ruby-githug `bisect` level.
+ * Android-native adaptation of the upstream ruby-githug `bisect` level.
  *
- * Setup documents the repository shape the learner explores. Evaluation is kept
- * state-based whenever the exercise changes repository objects; answer-only
- * levels intentionally validate the answer entered at the prompt.
+ * Upstream ships a Ruby fixture where `ruby prog.rb 5` should output 15.
+ * Android does not bundle Ruby, so this level keeps the same lesson and answer
+ * style but uses a POSIX shell test script committed into the exercise repo.
  */
 internal fun bisectLevel(): Level = level(
     id = "bisect",
     title = "Bisect",
-    description = "A bug was introduced somewhere along the way. You know that running `ruby prog.rb 5` should output 15. You can also run `make test`. What are the first 7 chars of the hash of the commit (the abbreviated hash) that introduced the bug?",
-    hints = emptyList(),
-    commandSuggestions = listOf("git bisect start", "make test"),
-    setup = { RepoState(initialized = true, branches = mapOf("master" to 7), commits = listOf(CommitNode("18ed2ac", "Introduce bug"))) },
-    validator = commitHashAnswer("18ed2ac"),
+    description = "A balance check started failing somewhere in the history. Run `./test-balance.sh` to test the current commit. Use `git bisect` to identify the first bad commit.",
+    hints = listOf(
+        "Start with a known bad commit and a known good commit.",
+        "`known-good` marks a commit where the balance check passes.",
+        "You can automate the search with `git bisect run ./test-balance.sh`.",
+    ),
+    commandSuggestions = listOf(
+        "./test-balance.sh",
+        "git bisect start HEAD known-good",
+        "git bisect run ./test-balance.sh",
+    ),
+    setup = {
+        RepoState(
+            initialized = true,
+            branches = mapOf("master" to 7),
+            tags = listOf("known-good"),
+            commits = listOf(
+                CommitNode("7", "Polish report labels"),
+                CommitNode("6", "Add forecast note"),
+                CommitNode("5", "Update help text"),
+                CommitNode("4", "Break closing balance calculation"),
+                CommitNode("3", "Add audit note"),
+                CommitNode("2", "Add January note"),
+                CommitNode("1", "Add balance check"),
+            ),
+        )
+    },
+    nativeSetup = {
+        resetFiles()
+        write("balance.txt", "BALANCE=100\n")
+        write(
+            "test-balance.sh",
+            """
+            |#!/bin/sh
+            |while IFS= read -r line
+            |do
+            |  if test "${'$'}line" = "BALANCE=100"
+            |  then
+            |    echo "balance ok"
+            |    exit 0
+            |  fi
+            |done < balance.txt
+            |echo "balance broken"
+            |exit 1
+            |""".trimMargin(),
+        )
+        addCommit("Add balance check", "balance.txt", "test-balance.sh")
+        tag("known-good")
+        write("notes.txt", "January review complete\n")
+        addCommit("Add January note", "notes.txt")
+        append("notes.txt", "Audit trail reviewed\n")
+        addCommit("Add audit note", "notes.txt")
+        write("balance.txt", "BALANCE=101\n")
+        addCommit("Break closing balance calculation", "balance.txt")
+        write("README", "Run ./test-balance.sh to check the report.\n")
+        addCommit("Update help text", "README")
+        append("notes.txt", "Forecast still depends on the balance check\n")
+        addCommit("Add forecast note", "notes.txt")
+        append("README", "Use git bisect to find the first broken commit.\n")
+        addCommit("Polish report labels", "README")
+        true
+    },
+    validator = { repo, command ->
+        val badCommit = repo.commits.firstOrNull { it.message == "Break closing balance calculation" }
+        val normalized = command.trim()
+        val answerMatches = badCommit != null &&
+            normalized.isNotBlank() &&
+            !normalized.startsWith("git ") &&
+            (normalized.startsWith(badCommit.id, ignoreCase = true) || badCommit.id.startsWith(normalized, ignoreCase = true))
+        val bisectFoundBadCommit = normalized.startsWith("git bisect run", ignoreCase = true) &&
+            "bisect-found" in repo.maintenanceActions
+        answerMatches || bisectFoundBadCommit
+    },
     testCases = listOf(
-        levelTestCase("answer bad commit", "18ed2ac"),
+        levelTestCase("automated bisect", "git bisect start HEAD known-good", "git bisect run ./test-balance.sh"),
     ),
 )

app/src/main/java/solutions/tretter/githugandroid/levels/CommitInFutureLevel.kt

@@ -10,12 +10,17 @@ package solutions.tretter.githugandroid
 internal fun commitInFutureLevel(): Level = level(
     id = "commit_in_future",
     title = "Commit In Future",
-    description = "Commit your changes with the future date (e.g. tomorrow).",
-    hints = listOf("Build a time format, and commit your code using --date parameter."),
-    commandSuggestions = listOf("git commit --date tomorrow -m \"Future commit\""),
+    description = "Commit your changes with a date later than the current system date.",
+    hints = listOf("Build a future timestamp, and commit your code using the --date parameter."),
+    commandSuggestions = listOf("git commit --date 2037-01-01T00:00:00+0000 -m \"Future commit\""),
     setup = { RepoState(initialized = true, files = listOf(GitFile("README", staged = true)), branches = mapOf("master" to 0)) },
-    validator = repoPredicate { repo -> repo.commits.isNotEmpty() },
+    validator = repoPredicate { repo ->
+        val nowSeconds = System.currentTimeMillis() / 1000
+        repo.commits.any { commit ->
+            commit.authorTimestampSeconds?.let { authorTime -> authorTime > nowSeconds } == true
+        }
+    },
     testCases = listOf(
-        levelTestCase("commit with date option", "git commit --date tomorrow -m \"Future commit\""),
+        levelTestCase("commit with date option", "git commit --date 2037-01-01T00:00:00+0000 -m \"Future commit\""),
     ),
 )

app/src/test/java/solutions/tretter/githugandroid/GitSandboxEngineTest.kt

@@ -411,6 +411,24 @@ class GitSandboxEngineTest {
         }
     }
 
+    @Test
+    fun nativeExecutableShortcutRunsScriptThroughShell() {
+        val git = testGitBinary()
+        assumeTrue(git.exists() && git.canExecute())
+        val root = Files.createTempDirectory("githug-script-shortcut").toFile()
+        try {
+            val runtime = GitRepositoryRuntime(root, git)
+            val level = bisectLevel()
+            val repo = runtime.prepareLevel(level)
+
+            val (_, output) = runtime.execute(level, repo, "./test-balance.sh")
+
+            assertTrue(output.joinToString("\n"), output.any { it.contains("balance broken") })
+        } finally {
+            root.deleteRecursively()
+        }
+    }
+
     private fun testGitBinary(): File {
         System.getenv("GITHUG_TEST_GIT_BINARY")
             ?.takeIf { it.isNotBlank() }

app/src/test/java/solutions/tretter/githugandroid/LevelSolutionsTest.kt

@@ -130,6 +130,15 @@ class LevelSolutionsTest {
             "Starting an interactive rebase without an upstream/range must not solve the reorder level.",
             reorderExercise.validator(bareInteractiveRebaseRepo, "git rebase -i"),
         )
+
+        val futureCommitExercise = commitInFutureLevel()
+        val futureCommitRuntime = GitRepositoryRuntime(runtimeRoot, gitBinary)
+        val futureCommitRepo = futureCommitRuntime.prepareLevel(futureCommitExercise)
+        val (currentDateCommitRepo, _) = futureCommitRuntime.execute(futureCommitExercise, futureCommitRepo, "git commit -m \"Current date commit\"")
+        assertFalse(
+            "A normal commit using the current system date must not solve the commit_in_future level.",
+            futureCommitExercise.validator(currentDateCommitRepo, "git commit -m \"Current date commit\""),
+        )
     }
 
     private companion object {
@@ -213,7 +222,7 @@ class LevelSolutionsTest {
                 appendLine("  <none>")
             } else {
                 commits.forEach { commit ->
-                    appendLine("  ${commit.id} ${commit.message}")
+                    appendLine("  ${commit.id} ${commit.authorTimestampSeconds ?: "unknown-time"} ${commit.message}")
                 }
             }
         }