Use Spectre to parse command-line arguments.

cli/Program.fs

@@ -1,42 +1,56 @@
 open System
 open System.IO
-open Argu
+open Spectre.Console
+open Spectre.Console.Cli
 
 open git_guts
 
 // --------------------------------------------------------------------
 
-type DumpPackFileArgs =
+let _getPackFilename packFilename repoDir =
-    | [<AltCommandLine("-f")>] Pack_Filename of packFilename:string
+    if packFilename <> "" then
-    interface IArgParserTemplate with
+        packFilename
-        member this.Usage =
+    else
-            match this with
+        // auto-detect pack files
-            | Pack_Filename _ -> "Pack file to dump."
+        let fnames = findRepoPacks repoDir
+        match fnames.Length with
+        | 0 -> failwith "No pack file was specified."
+        | 1 -> fnames.[0]
+        | _ -> failwith "Multiple pack files were found."
+
+// --------------------------------------------------------------------
 
-type CliArguments =
+type AppSettings() =
-    | [<AltCommandLine("-r")>] Repo of path:string
+    inherit CommandSettings()
-    | [<CliPrefix(CliPrefix.None)>] Dump_PackFile of ParseResults<DumpPackFileArgs>
+    [<CommandOption( "-r|--repo <GIT-REPO>" )>]
-    interface IArgParserTemplate with
+    member val RepoDir = "." with get, set
-        member this.Usage =
+    override this.Validate() =
-            match this with
+        this.RepoDir <- Path.GetFullPath( this.RepoDir )
-            | Repo _ -> "specify the git repo directory."
+        if not ( Directory.Exists this.RepoDir ) then
-            | Dump_PackFile _ -> "dump a pack file."
+            ValidationResult.Error( "Can't find git repo directory." )
+        else
+            ValidationResult.Success()
 
-type CliExiter() =
+// FUDGE! We need this for the settings in AppSettings to be recognized :-/
-    interface IExiter with
+type AppCommand() =
-        member __.Name = "CliExiter"
+    inherit Command<AppSettings>()
-        member __.Exit( msg, code ) =
+    override this.Execute( ctx, settings ) =
-            if code = ErrorCode.HelpText then
+        failwith "No command was specified."
-                // show the help text
+        0
-                printfn "%s" msg
+
-                exit 0
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-            else
+
-                // show the error message (sans help text)
+type DumpPackFileSettings() =
-                let pos = msg.IndexOf "USAGE:"
+    inherit AppSettings()
-                let msg2 = msg.Substring( 0, pos-1 )
+    [<CommandOption( "-f|--pack-file <PACK-FILE>" )>]
-                printfn "%s" msg2
+    member val PackFilename = "" with get, set
-                printfn "Use --help to get help."
+
-                exit 1
+type DumpPackFileCommand() =
+    inherit Command<DumpPackFileSettings>()
+    override this.Execute( ctx, settings ) =
+        let fname = _getPackFilename settings.PackFilename settings.RepoDir
+        dumpPackFile fname
+        0
 
 // --------------------------------------------------------------------
 
@@ -50,23 +64,11 @@ let main argv =
         disableSpectreCapabilities
 
     // parse the command-line arguments
-    let programName = System.AppDomain.CurrentDomain.FriendlyName
+    let app = CommandApp<AppCommand>()
-    let parser = ArgumentParser.Create<CliArguments>( programName=programName, helpTextMessage="Examine the guts of a git repo.", errorHandler=CliExiter() )
+    app.Configure( fun cfg ->
-    let parsedArgs = parser.Parse argv
+        cfg.SetApplicationName( System.AppDomain.CurrentDomain.FriendlyName ) |> ignore
-    let repoDir = Path.GetFullPath( parsedArgs.GetResult( Repo, defaultValue="." ) )
+        cfg.AddCommand<DumpPackFileCommand>( "dump-packfile" ).WithDescription(
-    if not ( Directory.Exists repoDir ) then
+            "Dump a pack file."
-        failwith "Can't find git repo directory."
+        ) |> ignore
-
+    )
-    // perform the requested action
+    app.Run( argv )
-    if parsedArgs.Contains Dump_PackFile then
-        // dump a pack file
-        let args = parsedArgs.GetResult Dump_PackFile
-        if not ( args.Contains Pack_Filename ) then
-            failwith "No pack file was specified." // nb: because [<Mandatory>] doesn't seem to work :-/
-        let fname = args.GetResult Pack_Filename
-        dumpPackFile fname
-    else
-        // no action was specified - print help
-        printfn "%s" ( parser.PrintUsage() )
-
-    0

cli/cli.fsproj

@@ -10,10 +10,6 @@
     <Compile Include="Program.fs" />
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="Argu" Version="6.1.1" />
-  </ItemGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\git-guts\git-guts.fsproj" />
   </ItemGroup>

git-guts/GitGuts.fs

@@ -69,3 +69,8 @@ module GitGuts =
         let buf = Array.zeroCreate 4
         inp.Read( buf, 0, 4 ) |> ignore
         ( int(buf.[0]) <<< 24 ) ||| ( int(buf.[1]) <<< 16 ) ||| ( int(buf.[2]) <<< 8 ) ||| int(buf.[3])
+
+    let findRepoPacks repoDir =
+        // find pack files in the git repo
+        let dname = Path.Combine( repoDir, ".git/objects/pack" )
+        Directory.GetFiles( dname, "*.pack" )

git-guts/tests/Utils.fs

@@ -104,8 +104,3 @@ module Utils =
     let runGitGc repoDir =
         // run git garbage collection
         runGit repoDir "gc" [] |> ignore
-
-    let findRepoPacks repoDir =
-        // find pack files in the git repo
-        let dname = Path.Combine( repoDir, ".git/objects/pack" )
-        Directory.GetFiles( dname, "*.pack" )