helper function for finding sh

command/alias_test.go

@@ -195,7 +195,7 @@ aliases:
 		t.Fatalf("unexpected error: %s", err)
 	}
 
-	expected := []string{"sh", "-c", "gh issue list | grep cool"}
+	expected := []string{"/usr/bin/sh", "-c", "gh issue list | grep cool"}
 
 	assert.Equal(t, expected, expanded)
 }
@@ -218,7 +218,7 @@ aliases:
 		t.Fatalf("unexpected error: %s", err)
 	}
 
-	expected := []string{"sh", "-c", "gh issue list --label=$1 | grep", "--", "bug", "foo"}
+	expected := []string{"/usr/bin/sh", "-c", "gh issue list --label=$1 | grep", "--", "bug", "foo"}
 
 	assert.Equal(t, expected, expanded)
 }

command/root.go

@@ -382,6 +382,32 @@ func ExecuteShellAlias(args []string) error {
 	return nil
 }
 
+func findSh() (string, error) {
+	shPath, err := exec.LookPath("sh")
+	if err == nil {
+		return shPath, nil
+	}
+
+	if runtime.GOOS == "windows" {
+		winNotFoundErr := errors.New("unable to locate sh to execute the shell alias with. The sh.exe interpreter is typically distributed with Git for Windows.")
+		// We can try and find a sh executable in a Git for Windows install
+		gitPath, err := exec.LookPath("git")
+		if err != nil {
+			return "", winNotFoundErr
+		}
+
+		shPath = filepath.Join(filepath.Dir(gitPath), "..", "bin", "sh.exe")
+		_, err = os.Stat(shPath)
+		if err != nil {
+			return "", winNotFoundErr
+		}
+
+		return shPath, nil
+	}
+
+	return "", errors.New("unable to locate sh to execute shell alias with")
+}
+
 // ExpandAlias processes argv to see if it should be rewritten according to a user's aliases. The
 // second return value indicates whether the alias should be executed in a new shell process instead
 // of running gh itself.
@@ -409,22 +435,14 @@ func ExpandAlias(args []string) (expanded []string, isShell bool, err error) {
 	if ok {
 		if strings.HasPrefix(expansion, "!") {
 			isShell = true
-			expanded = []string{"sh", "-c", expansion[1:]}
-			if runtime.GOOS == "windows" {
-				// Need to use absolute path for sh on windows
-				shPath, lookErr := exec.LookPath("sh")
-				if lookErr != nil {
-					gitPath, lookErr := exec.LookPath("git")
-					if lookErr != nil {
-						// TODO this error could be better probably
-						err = fmt.Errorf("unable to find sh. you will not be able to use shell aliases on this platform.")
-						return
-					}
-					shPath = filepath.Join(filepath.Dir(gitPath), "..", "bin", "sh.exe")
-				}
-				expanded[0] = shPath
+			shPath, shErr := findSh()
+			if shErr != nil {
+				err = shErr
+				return
 			}
 
+			expanded = []string{shPath, "-c", expansion[1:]}
+
 			if len(args[2:]) > 0 {
 				expanded = append(expanded, "--")
 				expanded = append(expanded, args[2:]...)