commit b6adedb6f92219b3795f616b46f18e752c5644be
from: Stefan Sperling <stsp@stsp.name>
date: Wed Oct 07 22:18:10 2020 UTC

fix line numbers in unidiff hunk headers and omit ",1"; matches diff(1)

commit - fde86f3da94e40ac11b0cd229348d7ae91456270
commit + b6adedb6f92219b3795f616b46f18e752c5644be
blob - da3c98842c7e864025e83544cc9206ac232c8289
blob + 649271a8542372b95f89e82a2a59f8814c6a24f6
--- lib/diff_output_unidiff.c
+++ lib/diff_output_unidiff.c
@@ -146,7 +146,7 @@ output_unidiff_chunk(struct diff_output_info *outinfo,
 		     const struct diff_result *result,
 		     const struct diff_chunk_context *cc)
 {
-	int rc;
+	int rc, left_start, left_len, right_start, right_len;
 	off_t outoff = 0, *offp;
 
 	if (diff_range_empty(&cc->left) && diff_range_empty(&cc->right))
@@ -183,9 +183,28 @@ output_unidiff_chunk(struct diff_output_info *outinfo,
 		state->header_printed = true;
 	}
 
-	rc = fprintf(dest, "@@ -%d,%d +%d,%d @@\n",
-		cc->left.start + 1, cc->left.end - cc->left.start,
-		cc->right.start + 1, cc->right.end - cc->right.start);
+	left_len = cc->left.end - cc->left.start;
+	if (left_len == 0 && cc->left.start > 0)
+		left_start = cc->left.start;
+	else
+		left_start = cc->left.start + 1;
+
+	right_len = cc->right.end - cc->right.start;
+	if (right_len == 0 && cc->right.start > 0)
+		right_start = cc->right.start;
+	else
+		right_start = cc->right.start + 1;
+
+	if (left_len == 1 && right_len != 1) {
+		rc = fprintf(dest, "@@ -%d +%d,%d @@\n",
+			left_start, right_start, right_len);
+	} else if (left_len != 1 && right_len == 1) {
+		rc = fprintf(dest, "@@ -%d,%d +%d @@\n",
+			left_start, left_len, right_start);
+	} else {
+		rc = fprintf(dest, "@@ -%d,%d +%d,%d @@\n",
+			left_start, left_len, right_start, right_len);
+	}
 	if (rc < 0)
 		return errno;
 	if (outinfo) {
blob - 12d576d9e937a74fa6092eb46826729a1c0f16fe
blob + c4dc6791528bf9a0cf786652ef20c3cc0aaa4659
--- test/expect008.diff
+++ test/expect008.diff
@@ -1,6 +1,6 @@
 --- test008.left.txt
 +++ test008.right.txt
-@@ -1,1 +1,6 @@
+@@ -1 +1,6 @@
  x
 +a
 +b