git: consolidate Git process creation

Not only does this reduce duplicate code, but it allows us to specify
the LC_CTYPE=C environment so we can parse the specific error message
made when creating an empty bundle.

Author: derrickstolee

internal/git/git.go

@@ -8,18 +8,28 @@ import (
 	"strings"
 )
 
-func GitCommand(args ...string) error {
-	git, lookErr := exec.LookPath("git")
-
-	if lookErr != nil {
-		return lookErr
+func GetExecCommand(args []string) (*exec.Cmd, error) {
+	git, err := exec.LookPath("git")
+	if err != nil {
+		return nil, fmt.Errorf("failed to find 'git' on the path: %w", err)
 	}
 
 	cmd := exec.Command(git, args...)
+	cmd.Env = append(cmd.Env, "LC_CTYPE=C")
+
+	return cmd, nil
+}
+
+func GitCommand(args ...string) error {
+	cmd, err := GetExecCommand(args)
+	if err != nil {
+		return err
+	}
+
 	cmd.Stderr = os.Stderr
 	cmd.Stdout = os.Stdout
 
-	err := cmd.Start()
+	err = cmd.Start()
 	if err != nil {
 		return fmt.Errorf("git command failed to start: %w", err)
 	}
@@ -33,26 +43,23 @@ func GitCommand(args ...string) error {
 }
 
 func GitCommandWithStdin(stdinLines []string, args ...string) error {
-	git, lookErr := exec.LookPath("git")
-
-	if lookErr != nil {
-		return lookErr
+	cmd, err := GetExecCommand(args)
+	if err != nil {
+		return err
 	}
 
 	buffer := bytes.Buffer{}
 	for line := range stdinLines {
 		buffer.Write([]byte(stdinLines[line] + "\n"))
 	}
 
-	cmd := exec.Command(git, args...)
-
 	cmd.Stdin = &buffer
 
 	errorBuffer := bytes.Buffer{}
 	cmd.Stderr = &errorBuffer
 	cmd.Stdout = os.Stdout
 
-	err := cmd.Start()
+	err = cmd.Start()
 	if err != nil {
 		return fmt.Errorf("git command failed to start: %w", err)
 	}