Allow semicolons to trail database names in "use"

Prior to this commit, the "use" command treated trailing semicolons as
significant parts of the database name. This lead to a confusing user
experience since other parts of influxql treat the trailing semicolon as
a statement separator, or appear to ignore it. A typical use case looks
something like:

> show databases;
-- snip --
> use foo;

This commit trims off trailing semicolons from database names in "use"
commands if present to match user expectations.

Fixes #2258

cmd/influx/main.go

@@ -321,7 +321,7 @@ func (c *CommandLine) SetAuth(cmd string) {
 }
 
 func (c *CommandLine) use(cmd string) {
-	args := strings.Split(strings.TrimSpace(cmd), " ")
+	args := strings.Split(strings.TrimSuffix(strings.TrimSpace(cmd), ";"), " ")
 	if len(args) != 2 {
 		fmt.Printf("Could not parse database name from %q.\n", cmd)
 		return

cmd/influx/main_test.go

@@ -75,13 +75,18 @@ func TestParseCommand_Use(t *testing.T) {
 		{cmd: "use db"},
 		{cmd: " use db"},
 		{cmd: "use db "},
+		{cmd: "use db;"},
 		{cmd: "Use db"},
 	}
 
 	for _, test := range tests {
 		if !c.ParseCommand(test.cmd) {
 			t.Fatalf(`Command "use" failed for %q.`, test.cmd)
 		}
+
+		if c.Database != "db" {
+			t.Fatalf(`Command "use" changed database to %q. Expected db`, c.Database)
+		}
 	}
 }