Subject: Re: [PATCH] pull: avoid running both merge and rebase

From: Junio C Hamano <[email-masked]>
Date: Fri, 27 Mar 2020 15:54:48 -0700

"Elijah Newren via GitGitGadget" <[email-masked]> writes:

> From: Elijah Newren <[email-masked]>
>
> When opt_rebase is true, we still first check if we can fast-forward.
> If the branch is fast-forwardable, then we can avoid the rebase and just
> use merge to do the fast-forward logic.  However, when commit a6d7eb2c7a
> ("pull: optionally rebase submodules (remote submodule changes only)",
> 2017-06-23) added the ability to rebase submodules it accidentally
> caused us to run BOTH a merge and a rebase.  Add a flag to avoid doing
> both.

This is a fun one.  Thanks for digging to the bottom of the issue.

> diff --git a/builtin/pull.c b/builtin/pull.c
> index 3e624d1e008..19899b45c1d 100644
> --- a/builtin/pull.c
> +++ b/builtin/pull.c
> @@ -976,6 +976,7 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
>  
>  	if (opt_rebase) {
>  		int ret = 0;
> +		int ran_ff = 0;
>  		if ((recurse_submodules == RECURSE_SUBMODULES_ON ||
>  		     recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND) &&
>  		    submodule_touches_in_range(the_repository, &rebase_fork_point, &curr_head))
> @@ -992,10 +993,12 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
>  			if (is_descendant_of(merge_head, list)) {
>  				/* we can fast-forward this without invoking rebase */
>  				opt_ff = "--ff-only";
> +				ran_ff = 1;
>  				ret = run_merge();
>  			}
>  		}
> -		ret = run_rebase(&curr_head, merge_heads.oid, &rebase_fork_point);
> +		if (!ran_ff)
> +			ret = run_rebase(&curr_head, merge_heads.oid, &rebase_fork_point);
>  
>  		if (!ret && (recurse_submodules == RECURSE_SUBMODULES_ON ||
>  			     recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND))
>
> base-commit: 274b9cc25322d9ee79aa8e6d4e86f0ffe5ced925