[PATCH] builtin/diff-files: convert ad hoc option parsing to parse-options API

[Edson <edsonwasswa54@gmail.com>]

The cmd_diff_files() function manually parses --base, --ours, --theirs,
and -q options using a hand-rolled loop with strcmp() calls. This is
error-prone and inconsistent with the rest of Git's codebase.

Convert this to use the parse-options API by:
- Adding option definitions using OPT_* macros
- Removing the manual parsing loop
- Using parse_options() for consistent argument handling

The --base, --ours, and --theirs options use PARSE_OPT_NONEG to prevent
negated forms (--no-base, etc.) which are not meaningful for merge stage
selection. This follows the pattern used in builtin/checkout.c for similar
stage selection options.

This makes the code more maintainable and brings it in line with Git's coding standards. It also enables auto-generated help text, git completion support, and option abbreviation.

Signed-off-by: Edson <edsonwasswa54@gmail.com>
---
 builtin/diff-files.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/builtin/diff-files.c b/builtin/diff-files.c
index ea91347ce2..a0c3981407 100644
--- a/builtin/diff-files.c
+++ b/builtin/diff-files.c
@@ -14,6 +14,7 @@
 #include "commit.h"
 #include "preload-index.h"
 #include "revision.h"
+#include "parse-options.h"
 
 static const char diff_files_usage[] =
 "git diff-files [-q] [-0 | -1 | -2 | -3 | -c | --cc] [<common-diff-options>] [<path>...]"
@@ -48,18 +49,21 @@ int cmd_diff_files(int argc,
 	prefix = precompose_argv_prefix(argc, argv, prefix);
 
 	argc = setup_revisions(argc, argv, &rev, NULL);
-	while (1 < argc && argv[1][0] == '-') {
-		if (!strcmp(argv[1], "--base"))
-			rev.max_count = 1;
-		else if (!strcmp(argv[1], "--ours"))
-			rev.max_count = 2;
-		else if (!strcmp(argv[1], "--theirs"))
-			rev.max_count = 3;
-		else if (!strcmp(argv[1], "-q"))
-			options |= DIFF_SILENT_ON_REMOVED;
-		else
-			usage(diff_files_usage);
-		argv++; argc--;
+
+	{
+		static struct option diff_files_options[] = {
+			OPT_SET_INT_F(0, "base", &rev.max_count,
+				      N_("show base version"), 1, PARSE_OPT_NONEG),
+			OPT_SET_INT_F(0, "ours", &rev.max_count,
+				      N_("show our version"), 2, PARSE_OPT_NONEG),
+			OPT_SET_INT_F(0, "theirs", &rev.max_count,
+				      N_("show their version"), 3, PARSE_OPT_NONEG),
+			OPT_BIT('q', NULL, &options,
+			       N_("be quiet"), DIFF_SILENT_ON_REMOVED),
+			OPT_END()
+		};
+		argc = parse_options(argc, argv, prefix, diff_files_options,
+				     diff_files_usage, 0);
 	}
 	if (!rev.diffopt.output_format)
 		rev.diffopt.output_format = DIFF_FORMAT_RAW;
-- 
2.46.0.windows.1