fix the description of set tag in dynamic-sql.xml doc

[xtyuns]

in the fact, <set> is equal to <trim prefix="set" prefixOverrides="," suffixOverrides=",">

ref: 95166a6#diff-df20f6a8f86025feb42cead35070d7689a4f04afc051008c93a2f38250bf53afR31

[harawata]

Thank you for the PR, @xtyuns !

Usually, you only need prefixOverrides or suffixOverrides, not both.
And, in this particular example, suffixOverrides is sufficient.

[xtyuns]

Hi @harawata, I understand what you mean, but what I pointed out is about the replacement of set tags and trim tags.
Please see the source of set tag:

mybatis-3/src/main/java/org/apache/ibatis/scripting/xmltags/SetSqlNode.java

Lines 26 to 34 in 0e20200

	public class SetSqlNode extends TrimSqlNode {
	private static final List<String> COMMA = Collections.singletonList(",");
	public SetSqlNode(Configuration configuration,SqlNode contents) {
	super(configuration, contents, "SET", COMMA, null, COMMA);
	}
	}

Because I encountered some problems in the process of using MyBatis, so I like to point out the errors in the documentation.

[harawata]

Hi @xtyuns ,

I see.
The behavior of <set /> tag was changed via #21 , actually.
So, the sentence might be a little bit confusing.

I am OK with rephrasing the sentence. For example:

Alternatively, you can achieve the same effect by using trim element.

I just don't think specifying both prefixOverrides and suffixOverrides is a good example.

I have reopened the PR, so you can add or force-push new commits to the same branch (patch-1).
If you prefer, you can close this PR and open a new PR.

Thank you!

[coveralls]

Coverage increased (+0.04%) to 87.283% when pulling 0d27a42 on xtyuns:patch-1 into ea4e829 on mybatis:master.

[xtyuns]

Ok, I open a new PR, so I closed this one.