respect branchNamePrefix config in all branch creation paths (#653)

The branchNamePrefix config setting was only being used when auto-generating
branch names via `av commit -b`, but not when using `av branch` directly or
`av branch --split` to split commits.

Now the prefix is applied consistently across all branch creation commands by
centralizing the logic in a single `applyBranchNamePrefix` helper function.
When branches are created (whether explicitly named or auto-generated), the
configured prefix gets prepended.

## Changes
- Added `applyBranchNamePrefix()` helper function to centralize prefix logic
- Applied prefix in `createBranch()` for `av branch <name>`
- Applied prefix in `branchSplit()` for `av branch --split`
- Removed duplicate prefix logic from `branchNameFromMessage()` in commit.go
- Updated test repos to explicitly set empty branchNamePrefix to avoid interference from global config

## Testing
- All existing tests pass
- Added comprehensive test coverage for branch name prefix behavior across all creation paths

Author: willschnicke-silkline

cmd/av/branch.go

@@ -8,6 +8,7 @@ import (
 
 	"emperror.dev/errors"
 	"github.com/aviator-co/av/internal/actions"
+	"github.com/aviator-co/av/internal/config"
 	"github.com/aviator-co/av/internal/git"
 	"github.com/aviator-co/av/internal/meta"
 	"github.com/aviator-co/av/internal/utils/cleanup"
@@ -181,6 +182,9 @@ func branchSplit(
 		newBranchName = sanitizeBranchName(lastCommit.Message)
 	}
 
+	// Apply branch name prefix
+	newBranchName = applyBranchNamePrefix(newBranchName)
+
 	// Get the parent of the last commit (HEAD~1)
 	parentCommitIter := lastCommit.Parents()
 	parentCommit, err := parentCommitIter.Next()
@@ -223,6 +227,14 @@ func branchSplit(
 	return nil
 }
 
+// applyBranchNamePrefix applies the configured branch name prefix to a branch name.
+func applyBranchNamePrefix(branchName string) string {
+	if config.Av.PullRequest.BranchNamePrefix != "" {
+		return config.Av.PullRequest.BranchNamePrefix + branchName
+	}
+	return branchName
+}
+
 // sanitizeBranchName creates a valid branch name from a string.
 func sanitizeBranchName(input string) string {
 	sanitized := strings.ToLower(strings.TrimSpace(input))
@@ -266,6 +278,9 @@ func createBranch(
 	branchName string,
 	parentBranchName string,
 ) (reterr error) {
+	// Apply branch name prefix
+	branchName = applyBranchNamePrefix(branchName)
+
 	// Determine important contextual information from Git
 	// or if a parent branch is provided, check it allows as a default branch
 	defaultBranch := repo.DefaultBranch()

cmd/av/commit.go

@@ -9,7 +9,6 @@ import (
 
 	"emperror.dev/errors"
 	"github.com/aviator-co/av/internal/actions"
-	"github.com/aviator-co/av/internal/config"
 	"github.com/aviator-co/av/internal/git"
 	"github.com/aviator-co/av/internal/meta"
 	"github.com/aviator-co/av/internal/utils/cleanup"
@@ -335,9 +334,6 @@ func branchNameFromMessage(message string) string {
 		name = name[:branchNameLength]
 	}
 	name = strings.ToLower(name)
-	if config.Av.PullRequest.BranchNamePrefix != "" {
-		name = fmt.Sprintf("%s%s", config.Av.PullRequest.BranchNamePrefix, name)
-	}
 	return name
 }
 

e2e_tests/branch_name_prefix_test.go

@@ -0,0 +1,95 @@
+package e2e_tests
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/aviator-co/av/internal/git/gittest"
+	"github.com/stretchr/testify/require"
+)
+
+// setupRepoWithPrefix creates a test repository with the specified branch name prefix.
+func setupRepoWithPrefix(t *testing.T, prefix string) *gittest.GitTestRepo {
+	t.Helper()
+	repo := gittest.NewTempRepo(t)
+	Chdir(t, repo.RepoDir)
+
+	configDir := filepath.Join(repo.RepoDir, ".git", "av")
+	require.NoError(t, os.MkdirAll(configDir, 0o755))
+	configFile := filepath.Join(configDir, "config.yml")
+	configContent := fmt.Sprintf("pullRequest:\n  branchNamePrefix: %q\n", prefix)
+	require.NoError(t, os.WriteFile(configFile, []byte(configContent), 0o644))
+
+	return repo
+}
+
+func TestBranchNamePrefixWithCommit(t *testing.T) {
+	repo := setupRepoWithPrefix(t, "user/myname/")
+
+	// Create a branch using av commit -b
+	repo.CreateFile(t, "test.txt", "test content")
+	repo.AddFile(t, "test.txt")
+	RequireAv(t, "commit", "-b", "-m", "test branch creation")
+
+	// Verify the branch name has the prefix
+	currentBranch := repo.Git(t, "branch", "--show-current")
+	require.Equal(t, "user/myname/test-branch-creation\n", currentBranch)
+}
+
+func TestBranchNamePrefixWithSplit(t *testing.T) {
+	repo := setupRepoWithPrefix(t, "feature/")
+
+	// Create a branch and make two commits
+	RequireAv(t, "branch", "base-branch")
+	repo.CommitFile(t, "file1.txt", "content1")
+	repo.CommitFile(t, "file2.txt", "content2")
+
+	// Split the last commit
+	RequireAv(t, "branch", "--split")
+
+	// Verify the new branch name has the exact expected prefix and sanitized name
+	currentBranch := repo.Git(t, "branch", "--show-current")
+	require.Equal(t, "feature/write-file2-txt\n", currentBranch)
+}
+
+func TestBranchNamePrefixWithExplicitName(t *testing.T) {
+	repo := setupRepoWithPrefix(t, "will/")
+
+	// Create a branch with explicit name using av branch
+	RequireAv(t, "branch", "test-branch")
+
+	// Verify the branch name has the prefix applied
+	currentBranch := repo.Git(t, "branch", "--show-current")
+	require.Equal(t, "will/test-branch\n", currentBranch)
+}
+
+func TestBranchNamePrefixWithSplitExplicitName(t *testing.T) {
+	repo := setupRepoWithPrefix(t, "user/dev/")
+
+	// Create a branch and make two commits
+	RequireAv(t, "branch", "base-branch")
+	repo.CommitFile(t, "file1.txt", "content1")
+	repo.CommitFile(t, "file2.txt", "content2")
+
+	// Split the last commit with explicit name
+	// Now the prefix SHOULD be applied to explicit names too for consistency
+	RequireAv(t, "branch", "--split", "my-explicit-branch")
+
+	// Verify the new branch name has the prefix applied
+	currentBranch := repo.Git(t, "branch", "--show-current")
+	require.Equal(t, "user/dev/my-explicit-branch\n", currentBranch)
+}
+
+func TestBranchNamePrefixEmpty(t *testing.T) {
+	repo := setupRepoWithPrefix(t, "")
+
+	repo.CreateFile(t, "test.txt", "test content")
+	repo.AddFile(t, "test.txt")
+	RequireAv(t, "commit", "-b", "-m", "test without prefix")
+
+	// Verify the branch name has no prefix
+	currentBranch := repo.Git(t, "branch", "--show-current")
+	require.Equal(t, "test-without-prefix\n", currentBranch)
+}

internal/git/gittest/repo.go

@@ -105,6 +105,8 @@ func NewTempRepoWithGitHubServer(t *testing.T, serverURL string) *GitTestRepo {
 github:
     token: "dummy_valid_token"
     baseUrl: %q
+pullRequest:
+    branchNamePrefix: ""
 `, serverURL),
 		0o644,
 	)