fix: use rev-parse instead of branch --show-current for older git compat (#303)

dist/index.js

@@ -363,8 +363,8 @@ exports.listAllFilesAsAdded = listAllFilesAsAdded;
 async function getCurrentRef() {
     core.startGroup(`Get current git ref`);
     try {
-        const branch = (await (0, exec_1.getExecOutput)('git', ['branch', '--show-current'])).stdout.trim();
-        if (branch) {
+        const branch = (await (0, exec_1.getExecOutput)('git', ['rev-parse', '--abbrev-ref', 'HEAD'])).stdout.trim();
+        if (branch && branch !== 'HEAD') {
             return branch;
         }
         const describe = await (0, exec_1.getExecOutput)('git', ['describe', '--tags', '--exact-match'], { ignoreReturnCode: true });

src/git.ts

@@ -166,8 +166,8 @@ export async function listAllFilesAsAdded(): Promise<File[]> {
 export async function getCurrentRef(): Promise<string> {
   core.startGroup(`Get current git ref`)
   try {
-    const branch = (await getExecOutput('git', ['branch', '--show-current'])).stdout.trim()
-    if (branch) {
+    const branch = (await getExecOutput('git', ['rev-parse', '--abbrev-ref', 'HEAD'])).stdout.trim()
+    if (branch && branch !== 'HEAD') {
       return branch
     }