[PATCH 3/3] Support branch^[merge] and branch^[push]

@@ -5,6 +5,7 @@
 #include "blob.h"
 #include "tree-walk.h"
 #include "refs.h"
+#include "remote.h"
 
 static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
 {

@@ -511,6 +512,51 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
 	return 0;
 }
 
+static int lookup_specials(const char *name, int len, unsigned char *sha1)
+{
+	const char *sp;
+
+	if (len < 5 || name[len - 1] != ']')
+		return -1;
+
+	for (sp = name + len - 1; name <= sp; sp--) {
+		int ch = *sp;
+		if (ch == '[' && name < sp && sp[-1] == '^')
+			break;
+	}
+
+	if (sp <= name)
+		return -1;
+
+	sp++; /* beginning of special name */
+	if (!strncmp("merge]", sp, 6)) {
+		char *word = xstrndup(name, sp - name - 2);
+		struct branch *branch = branch_get(word);
+		free(word);
+		if (branch && branch->merge) {
+			return get_sha1(branch->merge->dst, sha1);
+		}
+	} else if (!strncmp("push]", sp, 5)) {
+		char *word = xstrndup(name, sp - name - 2);
+		struct branch *branch = branch_get(word);
+		struct refspec remote;
+		struct refspec local;
+
+		if (!branch || !branch->remote)
+			return -1;
+
+		remote.src = branch->refname;
+		if (remote_find_push(branch->remote, &remote))
+			return -1;
+
+		local.src = remote.dst;
+		if (remote_find_tracking(branch->remote, &local))
+			return -1;
+		return get_sha1(local.dst, sha1);
+	}
+	return -1;
+}
+
 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 {
 	const char *cp;

@@ -565,6 +611,10 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1)
 		return get_nth_ancestor(name, len1, sha1, num);
 	}
 
+	ret = lookup_specials(name, len, sha1);
+	if (!ret)
+		return 0;
+
 	ret = peel_onion(name, len, sha1);
 	if (!ret)
 		return 0;