DEVELOPER_GUIDELINES: update about git amend

This is the result of Autumn workshop 2024

DEVELOPER_GUIDELINES.md

@@ -254,6 +254,19 @@ Ideally, we could have the following process, divided in 4 phases:
   marked with an `approved` label on Gitlab. The old `triage` label should be removed;
 - _Implementation_: Finally, the ticket gets implemented. This concludes the lifecycle.
 
+
+### Try to amend or squash if you rebase with `dev`
+
+Example here: https://gitlab.iscpif.fr/gargantext/haskell-gargantext/issues/322
+
+MR here: https://gitlab.iscpif.fr/gargantext/haskell-gargantext/merge_requests/258
+
+With amending/squashing, gitlab produces:
+- for new users on the issue, a large commit set with changes
+- for users already following the issue, gitlab produces a "compare
+  with previous version" like this one:
+  https://gitlab.iscpif.fr/gargantext/haskell-gargantext/merge_requests/258#note_9863
+
 ## Conclusion
 
 We have presented a comprehensive overview on the set of best practices we should put in place within