fix: resolve branch names case-insensitively against remote refs (#70)

When creating or checking out a branch, wt now queries `git ls-remote
--heads origin` and matches the user-provided branch name
case-insensitively. If the remote has a differently-cased branch (e.g.
`Feature/add-logging` vs `feature/add-logging`), wt uses the remote's
casing and prints a note to stderr.

Fixes #69

Author: timvw

main.go

@@ -388,6 +388,39 @@ func branchExists(branch string) bool {
 	return cmd.Run() == nil
 }
 
+// matchRemoteBranch parses git ls-remote --heads output and returns the
+// correctly-cased branch name if a case-insensitive match is found.
+// Returns the original branch name if no match is found.
+func matchRemoteBranch(branch string, lsRemoteOutput string) string {
+	lowerBranch := strings.ToLower(branch)
+	for _, line := range strings.Split(lsRemoteOutput, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		parts := strings.SplitN(line, "\t", 2)
+		if len(parts) != 2 {
+			continue
+		}
+		ref := strings.TrimPrefix(parts[1], "refs/heads/")
+		if strings.ToLower(ref) == lowerBranch {
+			return ref
+		}
+	}
+	return branch
+}
+
+// resolveRemoteBranchCase calls git ls-remote and resolves the branch name
+// using case-insensitive matching. Returns the remote's casing if found.
+func resolveRemoteBranchCase(branch string) string {
+	cmd := exec.Command("git", "ls-remote", "--heads", "origin")
+	output, err := cmd.Output()
+	if err != nil {
+		return branch
+	}
+	return matchRemoteBranch(branch, string(output))
+}
+
 func buildWorktreePath(info repoInfo, branch string) (string, error) {
 	rendered, err := renderWorktreePath(info, branch)
 	if err != nil {
@@ -867,6 +900,14 @@ var checkoutCmd = &cobra.Command{
 		} else {
 			branch = args[0]
 		}
+
+		// Resolve case-insensitive match against remote branches
+		resolved := resolveRemoteBranchCase(branch)
+		if resolved != branch {
+			fmt.Fprintf(os.Stderr, "Note: using remote branch name %q (you typed %q)\n", resolved, branch)
+			branch = resolved
+		}
+
 		info, err := getRepoInfo()
 		if err != nil {
 			return err
@@ -944,6 +985,13 @@ var createCmd = &cobra.Command{
 			base = args[1]
 		}
 
+		// Resolve case-insensitive match against remote branches
+		resolved := resolveRemoteBranchCase(branch)
+		if resolved != branch {
+			fmt.Fprintf(os.Stderr, "Note: using remote branch name %q (you typed %q)\n", resolved, branch)
+			branch = resolved
+		}
+
 		info, err := getRepoInfo()
 		if err != nil {
 			return err

main_test.go

@@ -1451,6 +1451,73 @@ func TestRunHooksEnvVarsAvailable(t *testing.T) {
 	}
 }
 
+func TestMatchRemoteBranch(t *testing.T) {
+	lsRemoteOutput := `abc123	refs/heads/main
+def456	refs/heads/Feature/add-logging
+ghi789	refs/heads/Feature/add-logging-v2
+jkl012	refs/heads/Bugfix/fixLogin
+mno345	refs/heads/develop
+`
+
+	tests := []struct {
+		name  string
+		input string
+		want  string
+	}{
+		{
+			name:  "Exact match returns as-is",
+			input: "Feature/add-logging",
+			want:  "Feature/add-logging",
+		},
+		{
+			name:  "Lowercase input matches uppercase remote",
+			input: "feature/add-logging",
+			want:  "Feature/add-logging",
+		},
+		{
+			name:  "All uppercase input matches mixed-case remote",
+			input: "FEATURE/ADD-LOGGING",
+			want:  "Feature/add-logging",
+		},
+		{
+			name:  "Case mismatch in middle of name",
+			input: "bugfix/fixlogin",
+			want:  "Bugfix/fixLogin",
+		},
+		{
+			name:  "No match returns original",
+			input: "nonexistent-branch",
+			want:  "nonexistent-branch",
+		},
+		{
+			name:  "Exact match for main",
+			input: "main",
+			want:  "main",
+		},
+		{
+			name:  "Partial name should not match",
+			input: "Feature/add",
+			want:  "Feature/add",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := matchRemoteBranch(tt.input, lsRemoteOutput)
+			if got != tt.want {
+				t.Errorf("matchRemoteBranch(%q) = %q, want %q", tt.input, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestMatchRemoteBranchEmptyOutput(t *testing.T) {
+	got := matchRemoteBranch("feature/foo", "")
+	if got != "feature/foo" {
+		t.Errorf("matchRemoteBranch with empty output = %q, want %q", got, "feature/foo")
+	}
+}
+
 func TestRunHooksMultiplePostContinueOnFailure(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping in short mode")