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From:
Mark Jamsek <mark@jamsek.com>
Subject:
Re: configurable diff algorithm for tog
To:
gameoftrees@openbsd.org
Date:
Fri, 1 Jul 2022 15:15:31 +1000

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On 22-07-01 12:15am, Stefan Sperling wrote:
> Make the diff algorithm used by 'tog diff' and 'tog blame' configurable.
> This allows people (like me) who prefer slow and tidy Patience diffs over
> quick and ugly Myers diffs to tell tog about this preference.
> 
> As a bonus, the diff algorithm can be toggled at run-time, in both the
> diff view and the blame view, by pressing the A key.
> 
> ok?

Nice! Works as described.

ok with or without tiny nit below

> diff 4b752015b5208a96c2d1b6c1c6b8589884b8b2b6 f86afd0cdf59e0214d28ee1b07f98b12e63650e2
> commit - 4b752015b5208a96c2d1b6c1c6b8589884b8b2b6
> commit + f86afd0cdf59e0214d28ee1b07f98b12e63650e2
> blob - 728ba5ee9e20edbde20ed7f0c2ff1cbabad89c0b
> blob + ed0412fd13daaa1ea18139730716db483ba49274
> --- tog/tog.1
> +++ tog/tog.1
> @@ -295,6 +295,12 @@ Find the Nth previous line which matches the current s
>  (default: 1).
>  .It Cm w
>  Toggle display of whitespace-only changes.
> +.It Cm A
> +Change the diff algorithm.
> +Supported diff algorithms are Myers and Patience. 
> +This is a global setting which also affects the
> +.Cm blame
> +view.
>  .El
>  .Pp
>  The options for
> @@ -379,6 +385,12 @@ Find the Nth next line which matches the current searc
>  .It Cm N
>  Find the Nth previous line which matches the current search pattern
>  (default: 1).
> +.It Cm A
> +Change the diff algorithm.
> +Supported diff algorithms are Myers and Patience. 
> +This is a global setting which also affects the
> +.Cm diff
> +view.
>  .El
>  .Pp
>  The options for
> @@ -560,7 +572,15 @@ work tree, use the repository path associated with thi
>  .El
>  .El
>  .Sh ENVIRONMENT
> -.Bl -tag -width TOG_COLORS
> +.Bl -tag -width TOG_DIFF_ALGORITHM
> +.It Ev TOG_DIFF_ALGORITHM
> +Determines the default diff algorithm used by
> +.Nm .
> +Valid values are
> +.Dq patience
> +and
> +.Dq myers .
> +If unset, the Myers diff algorithm will be used by default.
>  .It Ev TOG_COLORS
>  .Nm
>  shows colorized output if this variable is set to a non-empty value.
> blob - 800384dacf0faed4893832dd2760af45e28cb8c7
> blob + 5249c995a3b1c894615555cce80987087f672a75
> --- tog/tog.c
> +++ tog/tog.c
> @@ -136,7 +136,17 @@ STAILQ_HEAD(tog_colors, tog_color);
>  
>  static struct got_reflist_head tog_refs = TAILQ_HEAD_INITIALIZER(tog_refs);
>  static struct got_reflist_object_id_map *tog_refs_idmap;
> +static enum got_diff_algorithm tog_diff_algo = GOT_DIFF_ALGORITHM_MYERS;
>  
> +static void
> +switch_diff_algo(void)
> +{
> +	if (tog_diff_algo == GOT_DIFF_ALGORITHM_MYERS)
> +		tog_diff_algo = GOT_DIFF_ALGORITHM_PATIENCE;
> +	else
> +		tog_diff_algo = GOT_DIFF_ALGORITHM_MYERS;
> +}
> +
>  static const struct got_error *
>  tog_ref_cmp_by_name(void *arg, int *cmp, struct got_reference *re1,
>      struct got_reference* re2)
> @@ -321,7 +331,6 @@ struct tog_diff_view_state {
>  	int first_displayed_line;
>  	int last_displayed_line;
>  	int eof;
> -	enum got_diff_algorithm diff_algo;
>  	int diff_context;
>  	int ignore_whitespace;
>  	int force_text_diff;
> @@ -3966,13 +3975,13 @@ create_diff(struct tog_diff_view_state *s)
>  	case GOT_OBJ_TYPE_BLOB:
>  		err = got_diff_objects_as_blobs(&s->line_offsets, &s->nlines,
>  		    s->f1, s->f2, s->fd1, s->fd2, s->id1, s->id2,
> -		    s->label1, s->label2, s->diff_algo, s->diff_context,
> +		    s->label1, s->label2, tog_diff_algo, s->diff_context,
>  		    s->ignore_whitespace, s->force_text_diff, s->repo, s->f);
>  		break;
>  	case GOT_OBJ_TYPE_TREE:
>  		err = got_diff_objects_as_trees(&s->line_offsets, &s->nlines,
>  		    s->f1, s->f2, s->fd1, s->fd2, s->id1, s->id2, NULL, "", "",
> -		    s->diff_algo, s->diff_context, s->ignore_whitespace,
> +		    tog_diff_algo, s->diff_context, s->ignore_whitespace,
>  		    s->force_text_diff, s->repo, s->f);
>  		break;
>  	case GOT_OBJ_TYPE_COMMIT: {
> @@ -4008,7 +4017,7 @@ create_diff(struct tog_diff_view_state *s)
>  
>  		err = got_diff_objects_as_commits(&s->line_offsets, &s->nlines,
>  		    s->f1, s->f2, s->fd1, s->fd2, s->id1, s->id2, NULL,
> -		    s->diff_algo, s->diff_context, s->ignore_whitespace,
> +		    tog_diff_algo, s->diff_context, s->ignore_whitespace,
>  		    s->force_text_diff, s->repo, s->f);
>  		break;
>  	}
> @@ -4219,7 +4228,6 @@ open_diff_view(struct tog_view *view, struct got_objec
>  
>  	s->first_displayed_line = 1;
>  	s->last_displayed_line = view->nlines;
> -	s->diff_algo = GOT_DIFF_ALGORITHM_MYERS;
>  	s->diff_context = diff_context;
>  	s->ignore_whitespace = ignore_whitespace;
>  	s->force_text_diff = force_text_diff;
> @@ -4376,7 +4384,10 @@ input_diff_view(struct tog_view **new_view, struct tog
>  			view->count = 0;
>  		break;
>  	case 'a':
> +	case 'A':
>  	case 'w':
> +		if (ch == 'A')
> +			switch_diff_algo();
>  		if (ch == 'a')
>  			s->force_text_diff = !s->force_text_diff;
>  		if (ch == 'w')
> @@ -4950,7 +4961,7 @@ blame_thread(void *arg)
>  		goto done;
>  
>  	err = got_blame(ta->path, a->commit_id, ta->repo,
> -	    GOT_DIFF_ALGORITHM_MYERS, blame_cb, ta->cb_args,
> +	    tog_diff_algo, blame_cb, ta->cb_args,
>  	    ta->cancel_cb, ta->cancel_arg, fd1, fd2, f1, f2);
>  	if (err && err->code == GOT_ERR_CANCELLED)
>  		err = NULL;
> @@ -5455,6 +5466,18 @@ input_blame_view(struct tog_view **new_view, struct to
>  		else
>  			view->count = 0;
>  		break;
> +	case 'A':
> +		view->count = 0;
> +		switch_diff_algo();
> +		s->done = 1;
> +		thread_err = stop_blame(&s->blame);
> +		s->done = 0;
> +		if (thread_err)
> +			break;
> +		err = run_blame(view);
> +		if (err)
> +			break;
> +		break;

We could drop the `if (err)` check here as we break already.

>  	case 'c':
>  	case 'p': {
>  		struct got_object_id *id = NULL;
> @@ -7839,6 +7862,7 @@ main(int argc, char *argv[])
>  	    { "version", no_argument, NULL, 'V' },
>  	    { NULL, 0, NULL, 0}
>  	};
> +	char *diff_algo_str = NULL;
>  
>  	setlocale(LC_CTYPE, "");
>  
> @@ -7892,6 +7916,14 @@ main(int argc, char *argv[])
>  		}
>  	}
>  
> +	diff_algo_str = getenv("TOG_DIFF_ALGORITHM");
> +	if (diff_algo_str) {
> +		if (strcasecmp(diff_algo_str, "patience") == 0)
> +			tog_diff_algo = GOT_DIFF_ALGORITHM_PATIENCE;
> +		if (strcasecmp(diff_algo_str, "myers") == 0)
> +			tog_diff_algo = GOT_DIFF_ALGORITHM_MYERS;
> +	}
> +
>  	if (cmd == NULL) {
>  		if (argc != 1)
>  			usage(0, 1);
> 

-- 
Mark Jamsek <fnc.bsdbox.org>
GPG: F2FF 13DE 6A06 C471 CA80  E6E2 2930 DC66 86EE CF68