Hi Jonathan

On 24/08/2022 23:09, Jonathan Tan wrote:

"Phillip Wood via GitGitGadget" [off-list ref] writes:

quoted

@@ -1240,6 +1241,12 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
  		if (options.root)
  			die(_("options '%s' and '%s' cannot be used together"), "--keep-base", "--root");
  	}
+	/*
+	 * --keep-base defaults to --reapply-cherry-picks as it is confusing if
+	 * commits disappear when using this option.
+	 */
+	if (options.reapply_cherry_picks < 0)
+		options.reapply_cherry_picks = keep_base;

Here, we set options.reapply_cherry_picks to 1 if keep_base is 1, but...

quoted

@@ -1416,7 +1423,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
  	if (options.empty != EMPTY_UNSPECIFIED)
  		imply_merge(&options, "--empty");
  
-	if (options.reapply_cherry_picks)
+	/*
+	 * --keep-base implements --reapply-cherry-picks by altering upstream so
+	 * it works with both backends.
+	 */
+	if (options.reapply_cherry_picks && !keep_base)
  		imply_merge(&options, "--reapply-cherry-picks");

...if we implement --reapply-cherry-picks by altering upstream (and
hence not need to rely on the "merge" backend), shouldn't we suppress
the setting of options.reapply_cherry_picks too?

I'm not quite sure what you're suggesting. We only alter upstream if 
options.reapply_cherry_picks is true which happens below this hunk, are 
you saying we should clear options.reapply_cherry_picks when we change 
upstream? I'm not sure that has any practical effect as the left hand 
side of options.upstream...options.orig_head will be empty so when we do 
the revision walk to generate the todo list.

Best Wishes

Phillip