Add configurable timeout and retry for git network operations

Add per-attempt timeout (default 300s) and Kubernetes probe-style retry
configuration for git fetch, lfs-fetch, and ls-remote. New action inputs:
timeout, retry-max-attempts, retry-min-backoff, retry-max-backoff.

Fixes https://github.com/actions/checkout/issues/631

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -155,6 +155,28 @@ Please refer to the [release page](https://github.com/actions/checkout/releases/
     # Default: true
     set-safe-directory: ''
 
+    # Timeout in seconds for each git network operation attempt (fetch, lfs-fetch,
+    # ls-remote). If a single attempt exceeds this, it is killed and retried. Set to 0
+    # to disable. Default is 300 (5 minutes). Similar to Kubernetes probe
+    # timeoutSeconds.
+    # Default: 300
+    timeout: ''
+
+    # Maximum number of retry attempts for failed git network operations. Similar to
+    # Kubernetes probe failureThreshold.
+    # Default: 3
+    retry-max-attempts: ''
+
+    # Minimum backoff time in seconds between retry attempts. The actual backoff is
+    # randomly chosen between min and max. Similar to Kubernetes probe periodSeconds.
+    # Default: 10
+    retry-min-backoff: ''
+
+    # Maximum backoff time in seconds between retry attempts. The actual backoff is
+    # randomly chosen between min and max.
+    # Default: 20
+    retry-max-backoff: ''
+
     # The base URL for the GitHub instance that you are trying to clone from, will use
     # environment defaults to fetch from the same instance that the workflow is
     # running from unless specified. Example URLs are https://github.com or