diff --git a/action.yml b/action.yml
index ef3288b..cbec0bd 100644
--- a/action.yml
+++ b/action.yml
@@ -27,8 +27,9 @@ inputs:
     required: false
   body:
     description: >
-      Override the default generated PR body, the special string `{old_pull_request_id}` will be substituted
-      for the ID of the pull request which triggered the action
+      Override the default generated PR body. The special string `{old_pull_request_id}` will be substituted
+      for the ID of the pull request which triggered the action, and `{old_body}` will be substituted
+      for the body of the pull request which triggered the action.
     required: false
   labels:
     description: "A comma or newline separated list of labels."
diff --git a/dist/index.js b/dist/index.js
index a0b951b..0718fca 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -9195,6 +9195,7 @@ function createPullRequest(inputs, prBranch) {
                 // if the body comes from inputs, we replace {old_pull_request_id}
                 // to make it easy to reference the previous pull request in the new
                 body = body.replace('{old_pull_request_id}', pull_request.number.toString());
+                body = body.replace('{old_body}', pull_request.body ?? '');
             }
             core.info(`Using body '${body}'`);
             // Create PR
@@ -9383,7 +9384,16 @@ function run() {
             }
             // Take whatever is suggested by git if there are conflicts
             yield gitExecution(['add', '.'])
-            yield gitExecution(['commit', "--no-edit"])
+
+            // only commit if there are changes
+            const status = yield gitExecution(['status', '--porcelain']);
+            if (status.stdout.trim().length === 0) {
+                core.info('Working tree clean; skipping commit.');
+            }
+            else {
+                yield gitExecution(['commit', '--no-edit']);
+            }
+
             core.endGroup();
             // Push new branch
             core.startGroup('Push new branch to remote');
diff --git a/src/github-helper.ts b/src/github-helper.ts
index ad00fd6..e08cf8f 100644
--- a/src/github-helper.ts
+++ b/src/github-helper.ts
@@ -58,6 +58,9 @@ export async function createPullRequest(
         '{old_pull_request_id}',
         pull_request.number.toString()
       )
+      // replace {old_body} with the original PR body so callers can prepend
+      // or append text while still including the original description
+      body = body.replace('{old_body}', pull_request.body ?? '')
     }
     core.info(`Using body '${body}'`)
 
diff --git a/src/index.ts b/src/index.ts
index 799d355..dfe4518 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -75,7 +75,15 @@ export async function run(): Promise<void> {
     }
     // Take whatever is suggested by git if there are conflicts
     await gitExecution(['add', '.'])
-    await gitExecution(['commit'])
+
+    // only commit if there are changes
+    const status = await gitExecution(['status', '--porcelain'])
+    if (status.stdout.trim().length === 0) {
+      core.info('Working tree clean; skipping commit.')
+    } else {
+      await gitExecution(['commit', '--no-edit'])
+    }
+
     core.endGroup()
 
     // Push new branch