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[PATCH v5 3/4] Try normalizing files to avoid delete/modify conflicts when merging

From
Eyvind Bernhardsen <eyvind.bernhardsen@gmail.com>
Date
Jul 1, 2010, 09:09 UTC
Message-ID
<1081907f5a1044050c912e742b8500785dcc6b48.1277974452.git.eyvind.bernhardsen@gmail.com>
In-Reply-To
<cover.1277974452.git.eyvind.bernhardsen@gmail.com>

If a file is modified due to normalization on one branch, and deleted on another, a merge of the two branches will result in a delete/modify conflict for that file even if it is otherwise unchanged.

Try to avoid the conflict by normalizing and comparing the "base" file and the modified file when their sha1s differ. If they compare equal, the file is considered unmodified and is deleted.

Signed-off-by: Eyvind Bernhardsen <eyvind.bernhardsen@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 merge-recursive.c          |   51 ++++++++++++++++++++++++++++++++++++++++++-
 t/t6038-merge-text-auto.sh |    2 +-
 2 files changed, 50 insertions(+), 3 deletions(-)
diff --git a/merge-recursive.c b/merge-recursive.c
index 856e98c..4a84efe 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -1056,6 +1056,53 @@ static unsigned char *stage_sha(const unsigned char *sha, unsigned mode)
 	return (is_null_sha1(sha) || mode == 0) ? NULL: (unsigned char *)sha;
 }
 
+static int read_sha1_strbuf(const unsigned char *sha1, struct strbuf *dst)
+{
+	void *buf;
+	enum object_type type;
+	unsigned long size;
+	buf = read_sha1_file(sha1, &type, &size);
+	if (!buf)
+		return error("cannot read object %s", sha1_to_hex(sha1));
+	if (type != OBJ_BLOB) {
+		free(buf);
+		return error("object %s is not a blob", sha1_to_hex(sha1));
+	}
+	strbuf_attach(dst, buf, size, size + 1);
+	return 0;
+}
+
+static int blob_unchanged(const unsigned char *o_sha,
+			  const unsigned char *a_sha,
+			  const char *path)
+{
+	struct strbuf o = STRBUF_INIT;
+	struct strbuf a = STRBUF_INIT;
+	int ret = 0; /* assume changed for safety */
+
+	if (sha_eq(o_sha, a_sha))
+		return 1;
+	if (!core_merge_prefilter)
+		return 0;
+
+	assert(o_sha && a_sha);
+	if (read_sha1_strbuf(o_sha, &o) || read_sha1_strbuf(a_sha, &a))
+		goto error_return;
+	/*
+	 * Note: binary | is used so that both renormalizations are
+	 * performed.  Comparison can be skipped if both files are
+	 * unchanged since their sha1s have already been compared.
+	 */
+	if (renormalize_buffer(path, o.buf, o.len, &o) |
+	    renormalize_buffer(path, a.buf, o.len, &a))
+		ret = (o.len == a.len && !memcmp(o.buf, a.buf, o.len));
+
+error_return:
+	strbuf_release(&o);
+	strbuf_release(&a);
+	return ret;
+}
+
 /* Per entry merge function */
 static int process_entry(struct merge_options *o,
 			 const char *path, struct stage_data *entry)
@@ -1075,8 +1122,8 @@ static int process_entry(struct merge_options *o,
 	if (o_sha && (!a_sha || !b_sha)) {
 		/* Case A: Deleted in one */
 		if ((!a_sha && !b_sha) ||
-		    (sha_eq(a_sha, o_sha) && !b_sha) ||
-		    (!a_sha && sha_eq(b_sha, o_sha))) {
+		    (!b_sha && blob_unchanged(o_sha, a_sha, path)) ||
+		    (!a_sha && blob_unchanged(o_sha, b_sha, path))) {
 			/* Deleted in both or deleted in one and
 			 * unchanged in the other */
 			if (a_sha)
diff --git a/t/t6038-merge-text-auto.sh b/t/t6038-merge-text-auto.sh
index 1f2b3a8..1307ec0 100755
--- a/t/t6038-merge-text-auto.sh
+++ b/t/t6038-merge-text-auto.sh
@@ -46,7 +46,7 @@ test_expect_success 'Check merging addition of text=auto' '
 	test_cmp file file.temp
 '
 
-test_expect_failure 'Test delete/normalize conflict' '
+test_expect_success 'Test delete/normalize conflict' '
 	git checkout side &&
 	git reset --hard initial &&
 	git rm file &&
-- 
1.7.2.rc1.4.g09d06
Previous: Eyvind BernhardsenNext: Eyvind Bernhardsen
Message 12 of 13 in “Re-rolled merge normalization”
  1. 0/4 Re-rolled merge normalizationEyvind Bernhardsen, Jul 1, 2010
  2. 1/4 Avoid conflicts when merging branches with mixed normalizationEyvind Bernhardsen, Jul 1, 2010
  3. 2/4 Introduce "double conversion during merge" more graduallyEyvind Bernhardsen, Jul 1, 2010
  4. Johannes SixtJul 1, 2010
  5. Junio C HamanoJul 1, 2010
  6. Eyvind BernhardsenJul 1, 2010
  7. Jakub NarebskiJul 1, 2010
  8. Finn Arne GangstadJul 1, 2010
  9. Jakub NarebskiJul 1, 2010
  10. Eyvind BernhardsenJul 1, 2010
  11. Eyvind BernhardsenJul 1, 2010
  12. 3/4 Try normalizing files to avoid delete/modify conflicts when mergingEyvind Bernhardsen, Jul 1, 2010
  13. 4/4 Don't expand CRLFs when normalizing text during mergeEyvind Bernhardsen, Jul 1, 2010

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