Subject: Re: [RFC PATCH v1 06/17] merge-index: libify merge_one_path() and merge_all()

From: Phillip Wood <[email-masked]>
Date: Sun, 12 Jul 2020 19:02:32 +0100

Hi Alban

On 12/07/2020 12:36, Alban Gruin wrote:
> Hi Phillip,
> 
> Phillip Wood ([email-masked]) a écrit :
> 
>> Hi Alban
>>
>> On 25/06/2020 13:19, Alban Gruin wrote:
>> -%<-
>>> diff --git a/merge-strategies.c b/merge-strategies.c
>>> index 3a9fce9f22..f4c0b4acd6 100644
>>> --- a/merge-strategies.c
>>> +++ b/merge-strategies.c
>>> @@ -1,6 +1,7 @@
>>>  #include "cache.h"
>>>  #include "dir.h"
>>>  #include "merge-strategies.h"
>>> +#include "run-command.h"
>>>  #include "xdiff-interface.h"
>>>  
>>>  static int add_to_index_cacheinfo(struct index_state *istate,
>>> @@ -189,3 +190,101 @@ int merge_strategies_one_file(struct repository *r,
>>>  
>>>  	return 0;
>>>  }
>>> +
>>> +int merge_program_cb(const struct object_id *orig_blob,
>>> +		     const struct object_id *our_blob,
>>> +		     const struct object_id *their_blob, const char *path,
>>> +		     unsigned int orig_mode, unsigned int our_mode, unsigned int their_mode,
>>> +		     void *data)
>>
>> Using void* is slightly unfortunate but it's needed later.
>>
>> It would be nice to check if the program to run is git-merge-one-file
>> and call the appropriate function instead in that case so all users of
>> merge-index get the benefit of it being builtin. That probably wants to
>> be done in cmd_merge_index() rather than here though.
>>
> 
> Dunno, I am not completely comfortable with changing a parameter that 
> specifically describe a program, to a parameter that may be a program, 
> except in one case where `merge-index' should lock the index, setup the 
> worktree, and call a function instead.

There is some previous discussion about this at
https://lore.kernel.org/git/[email-masked]/

I'll try and have a proper look at your comments towards the end of the
week (or maybe the week after the way things are at the moment...)

Best Wishes

Phillip

> Well, I say that, but implementing that behaviour is not that hard:
> 
> -- snip --
> diff --git a/builtin/merge-index.c b/builtin/merge-index.c
> index 6cb666cc78..19fff9a113 100644
> --- a/builtin/merge-index.c
> +++ b/builtin/merge-index.c
> @@ -1,11 +1,15 @@
>  #define USE_THE_INDEX_COMPATIBILITY_MACROS
>  #include "builtin.h"
> +#include "lockfile.h"
>  #include "merge-strategies.h"
>  
>  int cmd_merge_index(int argc, const char **argv, const char *prefix)
>  {
>  	int i, force_file = 0, err = 0, one_shot = 0, quiet = 0;
>  	const char *pgm;
> +	void *data;
> +	merge_cb merge_action;
> +	struct lock_file lock = LOCK_INIT;
>  
>  	/* Without this we cannot rely on waitpid() to tell
>  	 * what happened to our children.
> @@ -26,7 +30,19 @@ int cmd_merge_index(int argc, const char **argv, const char *prefix)
>  		quiet = 1;
>  		i++;
>  	}
> +
>  	pgm = argv[i++];
> +	if (!strcmp(pgm, "git-merge-one-file")) {
> +		merge_action = merge_one_file_cb;
> +		data = (void *)the_repository;
> +
> +		setup_work_tree();
> +		hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
> +	} else {
> +		merge_action = merge_program_cb;
> +		data = (void *)pgm;
> +	}
> +
>  	for (; i < argc; i++) {
>  		const char *arg = argv[i];
>  		if (!force_file && *arg == '-') {
> @@ -36,13 +52,22 @@ int cmd_merge_index(int argc, const char **argv, const char *prefix)
>  			}
>  			if (!strcmp(arg, "-a")) {
>  				err |= merge_all(&the_index, one_shot, quiet,
> -						 merge_program_cb, (void *)pgm);
> +						 merge_action, data);
>  				continue;
>  			}
>  			die("git merge-index: unknown option %s", arg);
>  		}
>  		err |= merge_one_path(&the_index, one_shot, quiet, arg,
> -				      merge_program_cb, (void *)pgm);
> +				      merge_action, data);
> +	}
> +
> +	if (merge_action == merge_one_file_cb) {
> +		if (err) {
> +			rollback_lock_file(&lock);
> +			return err;
> +		}
> +
> +		return write_locked_index(&the_index, &lock, COMMIT_LOCK);
>  	}
>  	return err;
>  }
> -- snap --
> 
>>> +{
>>> +	char ownbuf[3][60] = {{0}};
>>
>> I know this is copied from above but it would be better to use
>> GIT_MAX_HEXSZ rather than 60
>>
> 
> Cheers,
> Alban
>