docs: Update HACKING guide with recommended git config

diff --git a/docs/HACKING.md b/docs/HACKING.md
index 1fbbed91d11d06078345fa6d5819efb03dcc27d8..ac4d6a69b049f94d86607476da972db44109a927 100644 (file)
--- a/docs/HACKING.md
+++ b/docs/HACKING.md
@@ -14,6 +14,14 @@ feature, please feel invited to fix it, and submit your work as a
 Please make sure to follow our [Coding Style](CODING_STYLE) when submitting
 patches. Also have a look at our [Contribution Guidelines](CONTRIBUTING).
 
+To start, run the following commands in the systemd git repository to set up
+git correctly:
+
+```shell
+$ git config submodule.recurse true
+$ git config fetch.recurseSubmodules on-demand
+```
+
 When adding new functionality, tests should be added. For shared functionality
 (in `src/basic/` and `src/shared/`) unit tests should be sufficient. The general
 policy is to keep tests in matching files underneath `src/test/`,