Grammar: Tidy up transaction statements in Snowflake dialect (#2196)

Co-authored-by: Barry Pollard <barry@tunetheweb.com>

src/sqlfluff/dialects/dialect_snowflake.py

@@ -3347,6 +3347,33 @@ class DescribeStatementSegment(BaseSegment):
     )
 
 
+@snowflake_dialect.segment(replace=True)
+class TransactionStatementSegment(BaseSegment):
+    """`BEGIN`, `START TRANSACTION`, `COMMIT`, AND `ROLLBACK` statement grammar.
+
+    Overwrites ANSI to match correct Snowflake grammar.
+
+    https://docs.snowflake.com/en/sql-reference/sql/begin.html
+    https://docs.snowflake.com/en/sql-reference/sql/commit.html
+    https://docs.snowflake.com/en/sql-reference/sql/rollback.html
+    """
+
+    match_grammar = OneOf(
+        Sequence(
+            "BEGIN",
+            OneOf("WORK", "TRANSACTION", optional=True),
+            Sequence("NAME", Ref("ObjectReferenceSegment"), optional=True),
+        ),
+        Sequence(
+            "START",
+            "TRANSACTION",
+            Sequence("NAME", Ref("ObjectReferenceSegment"), optional=True),
+        ),
+        "COMMIT",
+        "ROLLBACK",
+    )
+
+
 @snowflake_dialect.segment(replace=True)
 class TruncateStatementSegment(BaseSegment):
     """`TRUNCATE TABLE` statement.

test/fixtures/dialects/snowflake/snowflake_transactions.sql

@@ -0,0 +1,10 @@
+begin;
+begin work;
+begin transaction;
+begin name t4;
+begin work name t4;
+begin transaction name t4;
+start transaction;
+start transaction name t4;
+rollback;
+commit;

test/fixtures/dialects/snowflake/snowflake_transactions.yml

@@ -0,0 +1,65 @@
+# YML test files are auto-generated from SQL files and should not be edited by
+# hand. To help enforce this, the "hash" field in the file must match a hash
+# computed by SQLFluff when running the tests. Please run
+# `python test/generate_parse_fixture_yml.py`  to generate them after adding or
+# altering SQL files.
+_hash: edb9a85fc338df4d07be8e6d5881efc1fa5f83ff480d508ee17409dddbb99093
+file:
+- statement:
+    base:
+      keyword: begin
+- statement_terminator: ;
+- statement:
+    base:
+    - keyword: begin
+    - keyword: work
+- statement_terminator: ;
+- statement:
+    base:
+    - keyword: begin
+    - keyword: transaction
+- statement_terminator: ;
+- statement:
+    base:
+    - keyword: begin
+    - keyword: name
+    - object_reference:
+        identifier: t4
+- statement_terminator: ;
+- statement:
+    base:
+    - keyword: begin
+    - keyword: work
+    - keyword: name
+    - object_reference:
+        identifier: t4
+- statement_terminator: ;
+- statement:
+    base:
+    - keyword: begin
+    - keyword: transaction
+    - keyword: name
+    - object_reference:
+        identifier: t4
+- statement_terminator: ;
+- statement:
+    base:
+    - keyword: start
+    - keyword: transaction
+- statement_terminator: ;
+- statement:
+    base:
+    - keyword: start
+    - keyword: transaction
+    - keyword: name
+    - object_reference:
+        identifier: t4
+- statement_terminator: ;
+- statement:
+    base:
+      keyword: rollback
+- statement_terminator: ;
+- statement:
+    base:
+      keyword: commit
+- statement_terminator: ;