Merge branch 'jc/checkout-merge-base'

* jc/checkout-merge-base:
  rebase -i: teach --onto A...B syntax
  rebase: fix --onto A...B parsing and add tests
  "rebase --onto A...B" replays history on the merge base between A and B
  "checkout A...B" switches to the merge base between A and B

1 files changed, 42 insertions, 0 deletions

diff --git a/sha1_name.c b/sha1_name.c
index ca8f9dba94..1739e9e612 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -794,6 +794,48 @@ release_return:
 	return retval;
 }
 
+int get_sha1_mb(const char *name, unsigned char *sha1)
+{
+	struct commit *one, *two;
+	struct commit_list *mbs;
+	unsigned char sha1_tmp[20];
+	const char *dots;
+	int st;
+
+	dots = strstr(name, "...");
+	if (!dots)
+		return get_sha1(name, sha1);
+	if (dots == name)
+		st = get_sha1("HEAD", sha1_tmp);
+	else {
+		struct strbuf sb;
+		strbuf_init(&sb, dots - name);
+		strbuf_add(&sb, name, dots - name);
+		st = get_sha1(sb.buf, sha1_tmp);
+		strbuf_release(&sb);
+	}
+	if (st)
+		return st;
+	one = lookup_commit_reference_gently(sha1_tmp, 0);
+	if (!one)
+		return -1;
+
+	if (get_sha1(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
+		return -1;
+	two = lookup_commit_reference_gently(sha1_tmp, 0);
+	if (!two)
+		return -1;
+	mbs = get_merge_bases(one, two, 1);
+	if (!mbs || mbs->next)
+		st = -1;
+	else {
+		st = 0;
+		hashcpy(sha1, mbs->item->object.sha1);
+	}
+	free_commit_list(mbs);
+	return st;
+}
+
 /*
  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
  * notably "xyz^" for "parent of xyz"