diff-parseopt: convert --[no-]abbrev

OPT__ABBREV() has the same behavior as the deleted code with one
difference: it does check for valid number and error out if not. And the
'40' change is self explanatory.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -5254,6 +5254,7 @@ static void prep_parse_options(struct diff_options *options)
 		OPT_SET_INT('z', NULL, &options->line_termination,
 			    N_("do not munge pathnames and use NULs as output field terminators in --raw or --numstat"),
 			    0),
+		OPT__ABBREV(&options->abbrev),
 		OPT_CALLBACK_F(0, "output-indicator-new",
 			       &options->output_indicators[OUTPUT_INDICATOR_NEW],
 			       N_("<char>"),
@@ -5448,17 +5449,6 @@ int diff_opt_parse(struct diff_options *options,
 	}
 
 	/* misc options */
-	else if (!strcmp(arg, "--no-abbrev"))
-		options->abbrev = 0;
-	else if (!strcmp(arg, "--abbrev"))
-		options->abbrev = DEFAULT_ABBREV;
-	else if (skip_prefix(arg, "--abbrev=", &arg)) {
-		options->abbrev = strtoul(arg, NULL, 10);
-		if (options->abbrev < MINIMUM_ABBREV)
-			options->abbrev = MINIMUM_ABBREV;
-		else if (the_hash_algo->hexsz < options->abbrev)
-			options->abbrev = the_hash_algo->hexsz;
-	}
 	else if ((argcount = parse_long_opt("src-prefix", av, &optarg))) {
 		options->a_prefix = optarg;
 		return argcount;

parse-options-cb.c

@@ -22,8 +22,8 @@ int parse_opt_abbrev_cb(const struct option *opt, const char *arg, int unset)
 				     opt->long_name);
 		if (v && v < MINIMUM_ABBREV)
 			v = MINIMUM_ABBREV;
-		else if (v > 40)
-			v = 40;
+		else if (v > the_hash_algo->hexsz)
+			v = the_hash_algo->hexsz;
 	}
 	*(int *)(opt->value) = v;
 	return 0;