tools/patches/d2/expose_autoformat_subcommand.patch

diff --git a/.gitignore b/.gitignore
index 67d0886..7af7b35 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 .make-log
 .changed-files
 .make-log.txt
 *.got.json
 *.got.svg
 e2e_report.html
+bin
diff --git a/autofmt.go b/autofmt.go
new file mode 100644
index 0000000..749c079
--- /dev/null
+++ b/autofmt.go
@@ -0,0 +1,36 @@
+package main
+
+import (
+	"bytes"
+	"context"
+
+	"oss.terrastruct.com/xdefer"
+
+	"oss.terrastruct.com/d2/d2format"
+	"oss.terrastruct.com/d2/d2parser"
+	"oss.terrastruct.com/d2/lib/xmain"
+)
+
+func autofmt(ctx context.Context, ms *xmain.State) (err error) {
+	defer xdefer.Errorf(&err, "autofmt failed")
+
+	ms.Opts = xmain.NewOpts(ms.Env, ms.Log, ms.Opts.Flags.Args()[1:])
+	if len(ms.Opts.Args) == 0 {
+		return xmain.UsageErrorf("fmt must be passed the file to be formatted")
+	} else if len(ms.Opts.Args) > 1 {
+		return xmain.UsageErrorf("fmt only accepts one argument for the file to be formatted")
+	}
+
+	inputPath := ms.Opts.Args[0]
+	input, err := ms.ReadPath(inputPath)
+	if err != nil {
+		return err
+	}
+
+	m, err := d2parser.Parse(inputPath, bytes.NewReader(input), nil)
+	if err != nil {
+		return err
+	}
+
+	return ms.WritePath(inputPath, []byte(d2format.Format(m)))
+}
diff --git a/ci/dev.sh b/ci/dev.sh
new file mode 100755
index 0000000..cbc71bf
--- /dev/null
+++ b/ci/dev.sh
@@ -0,0 +1,7 @@
+#!/bin/sh
+set -eu
+cd -- "$(dirname "$0")/.."
+. ./ci/sub/lib.sh
+
+sh_c go build --tags=dev -o=bin/d2 .
+sh_c ./bin/d2 "$@"
diff --git a/ci/release/changelogs/next.md b/ci/release/changelogs/next.md
index 25d9930..5fdc99d 100644
--- a/ci/release/changelogs/next.md
+++ b/ci/release/changelogs/next.md
@@ -1,10 +1,12 @@
 #### Features 🚀
 
+- autoformat is supported on the CLI with the `fmt` subcommand.
+  [#292](https://github.com/terrastruct/d2/pull/292)
 - Latex is now supported. See [docs](https://d2lang.com/tour/text) for more.
   [#229](https://github.com/terrastruct/d2/pull/229)
 - `direction` keyword is now supported to specify `up`, `down`, `right`, `left` layouts. See
   [docs](https://d2lang.com/tour/layouts) for more.
   [#251](https://github.com/terrastruct/d2/pull/251)
 - Arrowhead labels are now supported. [#182](https://github.com/terrastruct/d2/pull/182)
 - `stroke-dash` on shapes is now supported. [#188](https://github.com/terrastruct/d2/issues/188)
 - `font-color` is now supported on shapes and connections. [#215](https://github.com/terrastruct/d2/pull/215)
diff --git a/ci/release/template/man/d2.1 b/ci/release/template/man/d2.1
index d46ca20..8347bd8 100644
--- a/ci/release/template/man/d2.1
+++ b/ci/release/template/man/d2.1
@@ -7,16 +7,18 @@
 .Sh SYNOPSIS
 .Nm d2
 .Op Fl -watch Ar false
 .Op Fl -theme Em 0
 .Ar file.d2
 .Op Ar file.svg | file.png
 .Nm d2
 .Ar layout Op Ar name
+.Nm d2
+.Ar fmt Ar file.d2
 .Sh DESCRIPTION
 .Nm
 compiles and renders
 .Ar file.d2
 to
 .Ar file.svg
 |
 .Ar file.png
@@ -70,13 +72,17 @@ Print usage information and exit.
 Print version information and exit.
 .El
 .Sh SUBCOMMANDS
 .Bl -tag -width Fl
 .It Ar layout
 Lists available layout engine options with short help.
 .It Ar layout Op Ar name
 Display long help for a particular layout engine.
+.It Ar fmt Ar file.d2
+Autoformat
+.Ar file.d2
+.Ns .
 .El
 .Sh SEE ALSO
 .Xr d2plugin-tala 1
 .Sh AUTHORS
 Terrastruct Inc.
diff --git a/help.go b/help.go
index 6c1cec8..aff1a72 100644
--- a/help.go
+++ b/help.go
@@ -10,34 +10,37 @@ import (
 	"strings"
 
 	"oss.terrastruct.com/d2/d2plugin"
 	"oss.terrastruct.com/d2/lib/xmain"
 )
 
 func help(ms *xmain.State) {
 	fmt.Fprintf(ms.Stdout, `Usage:
-  %s [--watch=false] [--theme=0] file.d2 [file.svg | file.png]
+  %[1]s [--watch=false] [--theme=0] file.d2 [file.svg | file.png]
+  %[1]s layout [name]
+  %[1]s fmt file.d2
 
 %[1]s compiles and renders file.d2 to file.svg | file.png
 It defaults to file.svg if an output path is not provided.
 
 Use - to have d2 read from stdin or write to stdout.
 
 See man d2 for more detailed docs.
 
 Flags:
 %s
 
 Subcommands:
   %[1]s layout - Lists available layout engine options with short help
-  %[1]s layout [layout name] - Display long help for a particular layout engine
+  %[1]s layout [name] - Display long help for a particular layout engine
+  %[1]s fmt file.d2 - Autoformat file.d2
 
 See more docs and the source code at https://oss.terrastruct.com/d2
-`, ms.Name, ms.Opts.Defaults())
+`, filepath.Base(ms.Name), ms.Opts.Defaults())
 }
 
 func layoutHelp(ctx context.Context, ms *xmain.State) error {
 	if len(ms.Opts.Flags.Args()) == 1 {
 		return shortLayoutHelp(ctx, ms)
 	} else if len(ms.Opts.Flags.Args()) == 2 {
 		return longLayoutHelp(ctx, ms)
 	} else {
diff --git a/lib/xmain/xmain.go b/lib/xmain/xmain.go
index 80de101..b0a1aeb 100644
--- a/lib/xmain/xmain.go
+++ b/lib/xmain/xmain.go
@@ -61,20 +61,20 @@ func Main(run RunFunc) {
 		} else if errors.As(err, &uerr) {
 			msg = err.Error()
 			usage = true
 		} else {
 			msg = err.Error()
 		}
 
 		if msg != "" {
+			ms.Log.Error.Print(msg)
 			if usage {
-				msg = fmt.Sprintf("%s\n%s", msg, "Run with --help to see usage.")
+				ms.Log.Error.Print("Run with --help to see usage.")
 			}
-			ms.Log.Error.Print(msg)
 		}
 		os.Exit(code)
 	}
 }
 
 type State struct {
 	Name string
 
diff --git a/main.go b/main.go
index 7586d08..bc183e4 100644
--- a/main.go
+++ b/main.go
@@ -60,28 +60,36 @@ func run(ctx context.Context, ms *xmain.State) (err error) {
 		return err
 	}
 
 	err = ms.Opts.Flags.Parse(ms.Opts.Args)
 	if !errors.Is(err, pflag.ErrHelp) && err != nil {
 		return xmain.UsageErrorf("failed to parse flags: %v", err)
 	}
 
+	if errors.Is(err, pflag.ErrHelp) {
+		help(ms)
+		return nil
+	}
+
 	if len(ms.Opts.Flags.Args()) > 0 {
 		switch ms.Opts.Flags.Arg(0) {
 		case "layout":
 			return layoutHelp(ctx, ms)
+		case "fmt":
+			return autofmt(ctx, ms)
+		case "version":
+			if len(ms.Opts.Flags.Args()) > 1 {
+				return xmain.UsageErrorf("version subcommand accepts no arguments")
+			}
+			fmt.Println(version.Version)
+			return nil
 		}
 	}
 
-	if errors.Is(err, pflag.ErrHelp) {
-		help(ms)
-		return nil
-	}
-
 	if *debugFlag {
 		ms.Env.Setenv("DEBUG", "1")
 	}
 
 	var inputPath string
 	var outputPath string
 
 	if len(ms.Opts.Flags.Args()) == 0 {
@@ -91,20 +99,16 @@ func run(ctx context.Context, ms *xmain.State) (err error) {
 		}
 		help(ms)
 		return nil
 	} else if len(ms.Opts.Flags.Args()) >= 3 {
 		return xmain.UsageErrorf("too many arguments passed")
 	}
 
 	if len(ms.Opts.Flags.Args()) >= 1 {
-		if ms.Opts.Flags.Arg(0) == "version" {
-			fmt.Println(version.Version)
-			return nil
-		}
 		inputPath = ms.Opts.Flags.Arg(0)
 	}
 	if len(ms.Opts.Flags.Args()) >= 2 {
 		outputPath = ms.Opts.Flags.Arg(1)
 	} else {
 		if inputPath == "-" {
 			outputPath = "-"
 		} else {