commit e4c510c1d83fe01247b6f59d855dffad81e4f26a
from: Stefan Sperling <stsp@stsp.name>
date: Sat Nov 21 15:10:29 2020 UTC

allow for telling the difference between empty and non-existent files

Adjust labels used in diff output accordingly; non-existent files
should have the label "/dev/null"

commit - e51ebd83fa731d197ee4074ee2e94dbc0581078c
commit + e4c510c1d83fe01247b6f59d855dffad81e4f26a
blob - e507bbb93de1346023e265fcae281efe13dd2ed5
blob + 6cd959e4159e40e5fcc467e4f69c7318fd54d3d5
--- include/diff_output.h
+++ include/diff_output.h
@@ -18,6 +18,11 @@
 struct diff_input_info {
 	const char *left_path;
 	const char *right_path;
+
+	/* Set by caller of diff_output_* functions. */
+	int flags;
+#define DIFF_INPUT_LEFT_NONEXISTENT	0x00000001
+#define DIFF_INPUT_RIGHT_NONEXISTENT	0x00000002
 };
 
 struct diff_output_info {
@@ -89,3 +94,6 @@ int diff_output_chunk_right_version(struct diff_output
 				const struct diff_input_info *info,
 				const struct diff_result *result,
 				const struct diff_chunk_context *cc);
+
+const char *diff_output_get_label_left(const struct diff_input_info *info);
+const char *diff_output_get_label_right(const struct diff_input_info *info);
blob - ad654fe1ca00262a9179746c88012cad9aedb134
blob + e286c6225a8b2095cd86a33a23e4c4031b3f3a0c
--- lib/diff_output.c
+++ lib/diff_output.c
@@ -325,4 +325,22 @@ diff_output_info_free(struct diff_output_info *output_
 {
 	ARRAYLIST_FREE(output_info->line_offsets);
 	free(output_info);
+}
+
+const char *
+diff_output_get_label_left(const struct diff_input_info *info)
+{
+	if (info->flags & DIFF_INPUT_LEFT_NONEXISTENT)
+		return "/dev/null";
+
+	return info->left_path ? : "a";
+}
+
+const char *
+diff_output_get_label_right(const struct diff_input_info *info)
+{
+	if (info->flags & DIFF_INPUT_RIGHT_NONEXISTENT)
+		return "/dev/null";
+
+	return info->right_path ? : "b";
 }
blob - 677f5baf44d4fa746fc192cb95326307b7f2bf0c
blob + 1c9b6d17294abf78edffde84b7937856f2620bb1
--- lib/diff_output_edscript.c
+++ lib/diff_output_edscript.c
@@ -139,8 +139,8 @@ diff_output_edscript(struct diff_output_info **output_
 				continue;
 
 			fprintf(dest, "Binary files %s and %s differ\n",
-			    info->left_path ? : "a",
-			    info->right_path ? : "b");
+			    diff_output_get_label_left(info),
+			    diff_output_get_label_right(info));
 			break;
 		}
 
blob - 520dc91d99494e5f4a3c9be8c238a6defd1ff48a
blob + 0c30eeafe6f5d012f49287395a528b8490816ccd
--- lib/diff_output_unidiff.c
+++ lib/diff_output_unidiff.c
@@ -235,7 +235,8 @@ output_unidiff_chunk(struct diff_output_info *outinfo,
 	}
 
 	if (print_header && !(state->header_printed)) {
-		rc = fprintf(dest, "--- %s\n", info->left_path ? : "a");
+		rc = fprintf(dest, "--- %s\n",
+		    diff_output_get_label_left(info));
 		if (rc < 0)
 			return errno;
 		if (outinfo) {
@@ -246,7 +247,8 @@ output_unidiff_chunk(struct diff_output_info *outinfo,
 			*offp = outoff;
 
 		}
-		rc = fprintf(dest, "+++ %s\n", info->right_path ? : "b");
+		rc = fprintf(dest, "+++ %s\n",
+		    diff_output_get_label_right(info));
 		if (rc < 0)
 			return errno;
 		if (outinfo) {
@@ -442,8 +444,8 @@ diff_output_unidiff(struct diff_output_info **output_i
 				continue;
 
 			fprintf(dest, "Binary files %s and %s differ\n",
-			    info->left_path ? : "a",
-			    info->right_path ? : "b");
+			    diff_output_get_label_left(info),
+			    diff_output_get_label_right(info));
 			break;
 		}