2 files changed, 95 insertions, 0 deletions

diff --git a/remote.c b/remote.c
index c8845746b6..a467d4ff07 100644
--- a/remote.c
+++ b/remote.c
@@ -1744,6 +1744,91 @@ const char *branch_get_upstream(struct branch *branch, struct strbuf *err)
 	return branch->merge[0]->dst;
 }
 
+static const char *tracking_for_push_dest(struct remote *remote,
+					  const char *refname,
+					  struct strbuf *err)
+{
+	char *ret;
+
+	ret = apply_refspecs(remote->fetch, remote->fetch_refspec_nr, refname);
+	if (!ret)
+		return error_buf(err,
+				 _("push destination '%s' on remote '%s' has no local tracking branch"),
+				 refname, remote->name);
+	return ret;
+}
+
+static const char *branch_get_push_1(struct branch *branch, struct strbuf *err)
+{
+	struct remote *remote;
+
+	if (!branch)
+		return error_buf(err, _("HEAD does not point to a branch"));
+
+	remote = remote_get(pushremote_for_branch(branch, NULL));
+	if (!remote)
+		return error_buf(err,
+				 _("branch '%s' has no remote for pushing"),
+				 branch->name);
+
+	if (remote->push_refspec_nr) {
+		char *dst;
+		const char *ret;
+
+		dst = apply_refspecs(remote->push, remote->push_refspec_nr,
+				     branch->refname);
+		if (!dst)
+			return error_buf(err,
+					 _("push refspecs for '%s' do not include '%s'"),
+					 remote->name, branch->name);
+
+		ret = tracking_for_push_dest(remote, dst, err);
+		free(dst);
+		return ret;
+	}
+
+	if (remote->mirror)
+		return tracking_for_push_dest(remote, branch->refname, err);
+
+	switch (push_default) {
+	case PUSH_DEFAULT_NOTHING:
+		return error_buf(err, _("push has no destination (push.default is 'nothing')"));
+
+	case PUSH_DEFAULT_MATCHING:
+	case PUSH_DEFAULT_CURRENT:
+		return tracking_for_push_dest(remote, branch->refname, err);
+
+	case PUSH_DEFAULT_UPSTREAM:
+		return branch_get_upstream(branch, err);
+
+	case PUSH_DEFAULT_UNSPECIFIED:
+	case PUSH_DEFAULT_SIMPLE:
+		{
+			const char *up, *cur;
+
+			up = branch_get_upstream(branch, err);
+			if (!up)
+				return NULL;
+			cur = tracking_for_push_dest(remote, branch->refname, err);
+			if (!cur)
+				return NULL;
+			if (strcmp(cur, up))
+				return error_buf(err,
+						 _("cannot resolve 'simple' push to a single destination"));
+			return cur;
+		}
+	}
+
+	die("BUG: unhandled push situation");
+}
+
+const char *branch_get_push(struct branch *branch, struct strbuf *err)
+{
+	if (!branch->push_tracking_ref)
+		branch->push_tracking_ref = branch_get_push_1(branch, err);
+	return branch->push_tracking_ref;
+}
+
 static int ignore_symref_update(const char *refname)
 {
 	unsigned char sha1[20];
diff --git a/remote.h b/remote.h
index 357a90963d..312b7ca131 100644
--- a/remote.h
+++ b/remote.h
@@ -209,6 +209,8 @@ struct branch {
 	struct refspec **merge;
 	int merge_nr;
 	int merge_alloc;
+
+	const char *push_tracking_ref;
 };
 
 struct branch *branch_get(const char *name);
@@ -229,6 +231,14 @@ int branch_merge_matches(struct branch *, int n, const char *);
  */
 const char *branch_get_upstream(struct branch *branch, struct strbuf *err);
 
+/**
+ * Return the tracking branch that corresponds to the ref we would push to
+ * given a bare `git push` while `branch` is checked out.
+ *
+ * The return value and `err` conventions match those of `branch_get_upstream`.
+ */
+const char *branch_get_push(struct branch *branch, struct strbuf *err);
+
 /* Flags to match_refs. */
 enum match_refs_flags {
 	MATCH_REFS_NONE		= 0,