Default download/install to ~/.msvc-go-wine when no dir is given

--dest (download) and the positional dir (install) were previously
required, forcing every user to pick and remember a location. Both now
default to a single hidden ~/.msvc-go-wine, matching the convention most
CLI tools use for their own data dir - still overridable for anyone who
wants a different location.

README.md

@@ -27,15 +27,16 @@ name it's invoked as (a "multi-call binary", like busybox):
 ## Quick start
 
 ```bash
-# 1. Download and unpack MSVC + Windows SDK (requires accepting Microsoft's
-#    Visual Studio Build Tools license, and msitools for unpacking .msi payloads)
-msvc-go-wine download --accept-license --dest ~/my_msvc
+# 1. Download and unpack MSVC + Windows SDK into ~/.msvc-go-wine (requires
+#    accepting Microsoft's Visual Studio Build Tools license, and msitools
+#    for unpacking .msi payloads). Pass --dest <dir> for a different location.
+msvc-go-wine download --accept-license
 
 # 2. Wire up the tool wrappers
-msvc-go-wine install ~/my_msvc
+msvc-go-wine install
 
 # 3. Add the toolchain to PATH and build
-export PATH=~/my_msvc/bin/x64:$PATH
+export PATH=~/.msvc-go-wine/bin/x64:$PATH
 cl /nologo /EHsc hello.cpp
 ```
 
@@ -55,12 +56,14 @@ pkcon install wine msitools
 ## Commands
 
 ```
-msvc-go-wine download --dest <dir> [options]   fetch and unpack MSVC/WinSDK
-msvc-go-wine install <dir>                     wire up wrappers for a downloaded MSVC
-msvc-go-wine env --bin <dir>/bin/<arch>        print INCLUDE/LIB for native clang-cl/lld-link use
-msvc-go-wine version                           print the version
+msvc-go-wine download --accept-license [--dest <dir>] [options]   fetch and unpack MSVC/WinSDK
+msvc-go-wine install [dir]                                        wire up wrappers for a downloaded MSVC
+msvc-go-wine env --bin <dir>/bin/<arch>                           print INCLUDE/LIB for native clang-cl/lld-link use
+msvc-go-wine version                                              print the version
 ```
 
+`--dest`/`[dir]` both default to `~/.msvc-go-wine` when omitted.
+
 `download` supports `--msvc-version`, `--sdk-version`, `--architecture`,
 `--host-arch`, `--with-*` component toggles, `--ignore`, `--only-download`,
 `--only-unpack`, `--keep-unpack`, `--cache`, `--language`,
@@ -73,7 +76,7 @@ You don't need Wine at all if you drive the (nonredistributable) MSVC/WinSDK
 headers and libraries with Clang/LLD in MSVC-compatible mode:
 
 ```bash
-eval "$(msvc-go-wine env --bin ~/my_msvc/bin/x64)"
+eval "$(msvc-go-wine env --bin ~/.msvc-go-wine/bin/x64)"
 clang-cl -c hello.c
 lld-link hello.obj -out:hello.exe
 ```

cmd/msvc-go-wine/download.go

@@ -13,7 +13,7 @@ import (
 
 func runDownload(args []string) int {
 	fs := flag.NewFlagSet("download", flag.ContinueOnError)
-	dest := fs.String("dest", "", "directory to install into (required unless --only-download)")
+	dest := fs.String("dest", "", "directory to install into (default: ~/.msvc-go-wine)")
 	cacheDir := fs.String("cache", "", "directory to use as a persistent download cache (default: a temp dir, removed afterwards)")
 	major := fs.Int("major", 18, "the major VS version to download")
 	preview := fs.Bool("preview", false, "download the preview/insiders channel instead of release/stable")
@@ -122,8 +122,13 @@ func runDownload(args []string) int {
 	}
 
 	if !*onlyDownload && *dest == "" {
-		fmt.Fprintln(os.Stderr, "msvc-go-wine download: --dest is required unless --only-download is set")
-		return 1
+		def, err := defaultToolchainDir()
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "msvc-go-wine download:", err)
+			return 1
+		}
+		*dest = def
+		fmt.Println("--dest not set, using default:", *dest)
 	}
 
 	if err := download.FetchPayloads(selected, cache, *onlyDownload); err != nil {

cmd/msvc-go-wine/install.go

@@ -8,11 +8,23 @@ import (
 )
 
 func runInstall(args []string) int {
-	if len(args) != 1 || args[0] == "-h" || args[0] == "--help" {
-		fmt.Fprintln(os.Stderr, "usage: msvc-go-wine install <dest>")
+	if len(args) > 1 || (len(args) == 1 && (args[0] == "-h" || args[0] == "--help")) {
+		fmt.Fprintln(os.Stderr, "usage: msvc-go-wine install [dest]  (default: ~/.msvc-go-wine)")
 		return 1
 	}
-	dest := args[0]
+
+	var dest string
+	if len(args) == 1 {
+		dest = args[0]
+	} else {
+		def, err := defaultToolchainDir()
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "msvc-go-wine install:", err)
+			return 1
+		}
+		dest = def
+		fmt.Println("No directory given, using default:", dest)
+	}
 
 	self, err := os.Executable()
 	if err != nil {

cmd/msvc-go-wine/main.go

@@ -63,11 +63,14 @@ func printUsage() {
 	fmt.Fprint(os.Stderr, `msvc-go-wine - cross compile with MSVC on Linux via Wine
 
 Usage:
-  msvc-go-wine download --dest <dir> [options]   fetch and unpack MSVC/WinSDK
-  msvc-go-wine install <dir>                     wire up wrappers for a downloaded MSVC
+  msvc-go-wine download --accept-license [--dest <dir>] [options]
+                                                  fetch and unpack MSVC/WinSDK
+  msvc-go-wine install [dir]                     wire up wrappers for a downloaded MSVC
   msvc-go-wine env --bin <dir/bin/arch>           print INCLUDE/LIB for native clang-cl/lld-link use
   msvc-go-wine version                           print the version
 
+--dest/[dir] default to ~/.msvc-go-wine if omitted.
+
 Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly:
   cl, link, lib, ml, ml64, mc, midl, mt, rc, dumpbin, msbuild, nmake, armasm, armasm64, cmd, findstr
 `)

cmd/msvc-go-wine/paths.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// defaultToolchainDir is where `download`/`install` operate when the user
+// doesn't specify a directory: a hidden ~/.msvc-go-wine, so it doesn't
+// clutter a plain `ls ~`.
+func defaultToolchainDir() (string, error) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(home, ".msvc-go-wine"), nil
+}