Add func and bats

bats/sql-branch.bats

@@ -0,0 +1,37 @@
+#!/usr/bin/env bats
+load $BATS_TEST_DIRNAME/helper/common.bash
+
+setup() {
+    setup_common
+
+    dolt sql <<SQL
+CREATE TABLE test (
+    pk int primary key
+);
+CREATE TABLE test2 (
+    pk int primary key
+);
+INSERT INTO test VALUES (0),(1),(2);
+SQL
+}
+
+teardown() {
+    assert_feature_version
+    teardown_common
+}
+
+@test "active_branch() func" {
+    run dolt sql -q 'select active_branch()' -r csv
+    [ $status -eq 0 ]
+    [[ "$output" =~ "active_branch()" ]] || false
+    [[ "$output" =~ "master" ]] || false
+}
+
+@test "active_branch() func on feature branch" {
+    run dolt branch tmp_br
+    run dolt checkout tmp_br
+    run dolt sql -q 'select active_branch()' -r csv
+    [ $status -eq 0 ]
+    [[ "$output" =~ "active_branch()" ]] || false
+    [[ "$output" =~ "tmp_br" ]] || false
+}

go/libraries/doltcore/sqle/dfunctions/active_branch.go

@@ -0,0 +1,96 @@
+// Copyright 2021 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package dfunctions
+
+import (
+	"fmt"
+	"github.com/dolthub/dolt/go/libraries/doltcore/ref"
+	"github.com/dolthub/go-mysql-server/sql"
+
+	"github.com/dolthub/dolt/go/libraries/doltcore/sqle"
+)
+
+const ActiveBranchFuncName = "active_branch"
+
+type ActiveBranchFunc struct {
+}
+
+// NewCommitFunc creates a new CommitFunc expression.
+func NewActiveBranchFunc() sql.Expression {
+	return &ActiveBranchFunc{}
+}
+
+// Eval implements the Expression interface.
+func (cf *ActiveBranchFunc) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
+	dbName := ctx.GetCurrentDatabase()
+	dSess := sqle.DSessFromSess(ctx.Session)
+
+	ddb, ok := dSess.GetDoltDB(dbName)
+
+	if !ok {
+		return nil, sql.ErrDatabaseNotFound.New(dbName)
+	}
+
+	rsr, ok := dSess.GetDoltDBRepoStateReader(dbName)
+
+	if !ok {
+		return nil, sql.ErrDatabaseNotFound.New(dbName)
+	}
+
+	currentBranch := rsr.CWBHeadRef()
+
+	branches, err := ddb.GetBranches(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, br := range(branches) {
+		if ref.Equals(br, currentBranch) {
+			return br.GetPath(), nil
+		}
+	}
+	return nil, fmt.Errorf("active branch not found")
+}
+
+// String implements the Stringer interface.
+func (cf *ActiveBranchFunc) String() string {
+	return fmt.Sprint("ACTIVE_BRANCH()")
+}
+
+// IsNullable implements the Expression interface.
+func (cf *ActiveBranchFunc) IsNullable() bool {
+	return false
+}
+
+// Resolved implements the Expression interface.
+func (*ActiveBranchFunc) Resolved() bool {
+	return true
+}
+
+func (cf *ActiveBranchFunc) Type() sql.Type {
+	return sql.Boolean
+}
+
+// Children implements the Expression interface.
+func (*ActiveBranchFunc) Children() []sql.Expression {
+	return nil
+}
+// WithChildren implements the Expression interface.
+func (v *ActiveBranchFunc) WithChildren(children ...sql.Expression) (sql.Expression, error) {
+	if len(children) != 0 {
+		return nil, sql.ErrInvalidChildrenNumber.New(v, len(children), 0)
+	}
+	return NewActiveBranchFunc(), nil
+}

go/libraries/doltcore/sqle/dfunctions/init.go

@@ -27,6 +27,7 @@ var DoltFunctions = []sql.Function{
 	sql.FunctionN{Name: DoltResetFuncName, Fn: NewDoltResetFunc},
 	sql.FunctionN{Name: DoltCheckoutFuncName, Fn: NewDoltCheckoutFunc},
 	sql.FunctionN{Name: DoltMergeFuncName, Fn: NewDoltMergeFunc},
+	sql.Function0{Name: ActiveBranchFuncName, Fn: NewActiveBranchFunc},
 }
 
 // These are the DoltFunctions that get exposed to Dolthub Api.