xec: Always set GIT_SPICE environment variable (#989)

Now that all os/exec usage has been centralized,
always set GIT_SPICE=1 for any subprocesses,
so that custom command and scripts
can do something useful with that.

Author: abhinav

.changes/unreleased/Added-20260111-113311.yaml

@@ -0,0 +1,7 @@
+kind: Added
+body: >-
+  git-spice now sets the `GIT_SPICE=1` environment variable
+  for all commands it spawns, including git, editors, etc.
+  This can be used, e.g., in git hooks to detect when they are
+  being run in the context of git-spice.
+time: 2026-01-11T11:33:11.036339-08:00

doc/mkdocs.yml

@@ -67,6 +67,10 @@ nav:
     - start/install.md
     - start/stack.md
     - start/submit.md
+  - Setting up: &setup
+    - setup/index.md
+    - setup/auth.md
+    - setup/shell.md
   - User Guide: &user-guide
     - guide/index.md
     - guide/concepts.md
@@ -75,10 +79,6 @@ nav:
     - guide/limits.md
     - guide/troubleshooting.md
     - guide/internals.md
-  - Setting up: &setup
-    - setup/index.md
-    - setup/auth.md
-    - setup/shell.md
   - CLI: &cli
     - cli/index.md
     - cli/reference.md

doc/src/setup/auth.md

@@ -185,7 +185,7 @@ Select an authentication method: {red}Personal Access Token{reset}
                 you want to use git-spice with
               - in the *Repository permissions* section,
                 grant **Read and write** access to **Pull requests** and **Contents**
-              - (<!-- gs:version 0.21.0 --> or higher)
+              - (<!-- gs:version v0.21.0 --> or higher)
                 in the *Organization permissions* section,
                 grant **Read-only** access to **Members**
 

help.go

@@ -82,6 +82,10 @@ func helpPrinter(_ kong.HelpOptions, ctx *kong.Context) error {
 		w.Print("Aliases can be combined to form shorthands for commands. For example:")
 		w.Printf("  %s bc => %s branch create", ctx.Model.Name, ctx.Model.Name)
 		w.Printf("  %s cc => %s commit create", ctx.Model.Name, ctx.Model.Name)
+
+		w.Print("")
+		w.Print("Environment variables:")
+		w.Print("  GIT_SPICE=1    Set for all commands spawned by git-spice")
 	}
 
 	return nil

internal/xec/cmd.go

@@ -19,6 +19,14 @@
 //
 //   - use Stderr to redirect stderr elsewhere
 //   - use WithLogPrefix to change the prefix for log messages
+//
+// # Environment variables
+//
+// All commands spawned via this package
+// always receive the environment variable "GIT_SPICE=1".
+//
+// Additional environment variables may be set
+// with the AppendEnv method.
 package xec
 
 import (
@@ -36,6 +44,8 @@ import (
 	"go.abhg.dev/gs/internal/silog"
 )
 
+const _gitSpiceEnv = "GIT_SPICE=1"
+
 var _osEnviron = os.Environ
 
 // Cmd is an external command being prepared or run.
@@ -63,7 +73,7 @@ func Command(ctx context.Context, log *silog.Logger, name string, args ...string
 	stderr, wrap := outputLogWriter("stderr", logger)
 	cmd := exec.CommandContext(ctx, name, args...)
 	cmd.Stderr = stderr
-	cmd.Env = _osEnviron()
+	cmd.Env = append(_osEnviron(), _gitSpiceEnv)
 	return &Cmd{
 		cmd:     cmd,
 		log:     logger,

internal/xec/cmd_test.go

@@ -179,6 +179,14 @@ func TestCmd_AppendEnv(t *testing.T) {
 		require.NoError(t, err)
 		assert.Equal(t, "value1 value2", output)
 	})
+
+	t.Run("GitSpiceExecSet", func(t *testing.T) {
+		cmd := Command(ctx, log, "sh", "-c", "echo $GIT_SPICE")
+
+		output, err := cmd.OutputChomp()
+		require.NoError(t, err)
+		assert.Equal(t, "1", output)
+	})
 }
 
 func TestCmd_Run(t *testing.T) {

internal/xec/edit.go

@@ -1,6 +1,9 @@
 package xec
 
-import "os/exec"
+import (
+	"os"
+	"os/exec"
+)
 
 // EditCommand constructs a command to open the editor
 // with the given editor command.
@@ -16,5 +19,6 @@ func EditCommand(editCmd string, args ...string) *exec.Cmd {
 		args = append([]string{"-c", editCmd + ` "$@"`, "--"}, args...)
 		cmd = exec.Command("sh", args...)
 	}
+	cmd.Env = append(os.Environ(), _gitSpiceEnv)
 	return cmd
 }

internal/xec/edit_test.go

@@ -0,0 +1,37 @@
+package xec
+
+import (
+	"fmt"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEditCommand_setsGitSpiceExec(t *testing.T) {
+	// Subprocess mode: print GIT_SPICE value and exit.
+	if os.Getenv("INSIDE_TEST") == "1" {
+		fmt.Print(os.Getenv("GIT_SPICE"))
+		os.Exit(0)
+	}
+
+	t.Run("SimpleEditor", func(t *testing.T) {
+		cmd := EditCommand(_testBinary, "-test.run", "^"+t.Name()+"$")
+		cmd.Env = append(cmd.Env, "INSIDE_TEST=1")
+
+		output, err := cmd.Output()
+		require.NoError(t, err)
+		assert.Equal(t, "1", string(output))
+	})
+
+	t.Run("ShellEditor", func(t *testing.T) {
+		cmd := EditCommand(fmt.Sprintf("%q -test.run '^%s$'", _testBinary, t.Name()))
+		cmd.Env = append(cmd.Env, "INSIDE_TEST=1")
+		cmd.Stderr = t.Output()
+
+		output, err := cmd.Output()
+		require.NoError(t, err)
+		assert.Equal(t, "1", string(output))
+	})
+}

testdata/help/gs.txt

@@ -80,3 +80,6 @@ Run "gs <command> --help" for more information on a command.
 Aliases can be combined to form shorthands for commands. For example:
   gs bc => gs branch create
   gs cc => gs commit create
+
+Environment variables:
+  GIT_SPICE=1    Set for all commands spawned by git-spice